A POLISH HUT FROM THE POINT OF VIEW OF ENERGY EFFICIENCY

Mirosława Górecka
Department of Civil Engineering and Geodesy, Warsaw University of Life Sciences - SGGW

ABSTRACT

The paper is dedicated to the development of a traditional Polish hut from the point of view of energy efficiency. There were emphasized such elements of the building architecture, as: its mass (including the spatial form of a roof), the arrangement of rooms and functional connections, the application of material and constructive solutions as well as the location at a building plot. The trends from the whole area of Poland were confronted with the examinations of some chosen huts at the area of the northern Casubia. It has been stated that the folk architecture, which is a result of the work of numerous generations and is characterized with a skilled adaptation to the natural environment and climate conditions, should become a pattern and inspiration to seek low energy-consuming solutions during the designing of country dwelling houses.

Key words: Polish hut, energy efficiency.

INTRODUCTION

Optimal thermal conditions have always been one of the most important factor for a human, deciding of the choice of a localization of living place. With time, this place assumed the name of house, widely understood – i.e. a space, which can be organized according to the most important existential needs. There must be count a security need, including the need of the adaptation of a house to climate conditions, i.e. to find shelter from a disadvantageous influence of weather. The priorities and directives applying nowadays to a building design are the result of the thousand-year quest of effective solutions in architecture. Another result of this quest is a plenty of various material and constructive solutions which arise mainly due to the adaptation of a house to local conditions.

The rational usage of energy, aimed at its minimization, is the most important rule of designing, realization and usage of a low energy-consuming building. It is characterized by a relatively low energy demand in the whole technical life cycle, i.e. from raising materials, through transportation and building, to the exploitation and liquidation.

The houses used to be constructed nowadays, characterized by the rational usage of energy, should draw inspiration i.a. from a rustical hut – the basic pattern of the traditional Polish folk architecture. The analysis of a homestead architecture as well as the modern houses, which are used to be constructed according to the rules of balanced development, shows that these buildings have surprisingly many of common features. Thus, it is worth using the experience and wisdom of previous generations. How much costs a senseless breaking off with tradition – the users of houses arisen on the country in the 2^nd half of 20^th century know it. The houses are difficult to warm up not only due to the improper materials, but also uneconomic architectural solutions.

METHOD OF RESEARCH

The article is in the character of a report from a scientific-research work concerning a problem connected to a low energy-consuming country house. On account of the sort of the problem being into consideration the paper bases on two types of research: direct and indirect one.

The indirect research, which use a monographic method consisting in a critical analysis of the specialist literature, involve a subject of specificity of construction of a country house as well as low energy-consuming building.

The direct research concerning an existing country housing were carried out in certain chosen countries in the region particularly close to the Author – seaside Casubia. This region had been chosen among others on the account of the specific climate conditions as well as of the big number of the preserved historical houses, whose examples served to the analysis of the architecture in the context of energy efficiency.

In the research concerning the existing objects, an empirical method was used, which consisted in the analysis of the chosen elements of architecture, affecting the energy efficiency of the houses (the building mass including the spatial shape of a roof, the construction of rooms and functional connections, the application of material and constructive solutions, the localization at a building plot). An observation technique was used, whereas the descriptions of specific architectural solutions, connected to the appropriate illustrative material (Author's photos and drawings), were assumed as the necessary method to the visible depiction of the topic being considered in the paper.

In the direct research, a case study was used as a research method, which lets to draw conclusions related to the features of the buildings chosen and being characterized, their technical conditions and other reasons and results concerning their functioning.

THE RULES OF CONSTRUCTION OF LOW ENERGY-CONSUMING ARCHITECTURAL SOLUTIONS OF POLISH HUT

The basic feature of Polish folk building is a consequent logic of build actions, as: the adaptation of buildings' arrangement to their function, the ideal compliance of a form with materials and construction, and mainly – the adaptation of the objects to the natural environment and climate conditions.

The concern for the saving of a house from cold, wind and rain unpleasantness is visible in the forming of a country hut architecture. It seems that these elements, which had an influence on a building energy efficiency, are worth to distinguish. There will be also useful to point the possibilities of their application in the modern dwelling houses on the country, of the Polish features and native expression.

The review of the traditional types of a Polish country house confirms that its form indeed depends on the nature forces – allied and antagonistic – felt stronger at an open terrain than in big urban agglomerations. The efforts of a constructor had been directed mainly at using of the favorable forces and weakening of the unpleasant ones [8].

The adaptation of houses to the environment and climate conditions, made by people, is visible in the shape of huts – in the basic elements of their construction, as:

• the building mass and the shape of a roof (the roof slope angle, eaves reach),

• the space arrangement,

• material and constructive solutions (thermal insulation parameters of walls and ceilings, location and magnitude of window and door openings) [3].

Wind and precipitation affected the roof construction, its spatial shape, roof slope angle, magnitude of eaves and the way of roofing. Low temperatures and their diurnal variations affected also the rooms' arrangement and the division on the cold and warm zone, the choice of the materials for a wall construction as well as the creation of original heating systems in the particular regions of the country. The usage of insolation was the main reason of the wall orientation and the arrangement of door and window openings in the buildings. The wind directions determined the localization of an entrance door and influenced the way of installation of shields and flues.

The country buildings are characterized by the mass cohesion, what affects generally more advantageous heating conditions. This solution has an influence at the reduction of the external fabric, first of all – external walls, because precisely through them the most of heat escapes from a building. Simultaneously, the usage of materials and labor itself is reduced during the construction.

In the folk architecture, the essential factor affecting the energy efficiency, building mass and the architectural expression of the house connected to it, was a high roof and first of all, its magnitude, shape and appropriately chosen proportions in the relation with walls. If a roofing material was proper, the roof slope angle, favoring a fast water flow and snow sliding, as well as the reach of eaves beyond the walls, were almost directly proportional to the amount of precipitation in a given region of the country [2].

An attic in a country house constituted a good isolator of a ground floor and generally was not used for residential purposes, and only sometimes served as a fodder or crops magazine. Thus, constructors were not restricted by the destination of the attic during construction of a roof spatial form.

The roof mass was shaped mainly according to climate conditions, but not only. Also the economic accounts were important as well as the landscape character, the sort of roof constructions being used in a given region, roofing watertightness. In the traditional folk architecture, the material of roofing was straw and reed. Straw thatches, light and good thermal isolators, dominated in the central and southern zones of Poland, i.e. in the regions with agricultural cultivation. On the other hand, a reed roofing was used mainly on the north of the country (Lake District, Pomerania) [8]. It was long-lasting and resistant to putrefaction.

A characteristic roof element, playing a role of arcades and – first of all – preserving the walls from damping due to precipitations, were eaves. Its role was often also give a protection of an entrance to the house. Simultaneously, it formed a microclimate around the building and in sunny days threw a deep horizontal shape, what protected the rooms from an overheating in summer. Rafters of protruding eaves were often a masterpiece of carpentry. The special type of the eaves were so-called arcade eaves, used mainly alongside the shorter wall of a building, whereas more rarely – alongside the longer one. It could even reach 1.5 m of length [9].

The next characteristic elements in country architecture, having an essential influence at the increase of the object's energy efficiency, were arcades and porches. They played an important role of the protection of the building entrance from precipitations, wind and – in summer – the sun. They enriched an architectural form of buildings, having simultaneously practical functions. They were the proof of the high level of carpentry, of the concern for a buildings' external look as well as of the intentional space organization. A certain type of the attic had a form of strongly protruding eaves. In the folk architecture, there can be distinguished the types of attic as follows: alongside a shorter (gable) wall, a longer (eaves) wall and more rarely – quoin attic. The attic was a place dedicated to make domestic and handicraft works as well as to have a rest. A porch, supported at carved posts, was the element of a pure entrance, having various size and form.

An energy efficiency in the folk architecture manifested itself also in the arrangement of rooms in the house. Their height was not big – about 2.2 m, what also affected the heat economy. In the various regions of the country, a different arrangement of a dwell house had been formed, which depended not only on functional accounts or local tradition, but mainly – as it occurs – on climate conditions. The territorial traditional arrangement of buildings can be classified into three groups: one-duct, one-and-half-duct, two-duct. The fact deserves special attention, that the one-duct arrangements occurred mainly in the southern, south-eastern and partly central regions of Poland, whereas two-duct arrangements – in northern and north-eastern voivodships, where an average daily temperature is lower and winter lasts for a longer time in year. It is justified because a two-duct arrangement is more advantageous due to an energetic characteristics. Simultaneously, in the greater part of the northern Poland predominated buildings of a concentrated arrangement, at a square plan. In the southern part, on the other hand, the houses were characterized by an elongated shape. The number of ducts as well as the length and width of the building had an essential influence at the shape of a roof and its proportions related to walls.

The arrangement of rooms was adopted to various climate conditions and work organization in winter and summer, what was visible through the varying functions of residential rooms, mainly a kitchen and hall [7]. The latter, however, had mainly a task of protecting a residence room from the influence of atmospheric factors.

The oldest and the simplest dwelling country houses were single-room houses, containing of two rooms: hall and living quarter. As an effect of that a fire facility was being more and more extended and surrounded by auxiliary rooms, there were occurring: a room behind a stove, a chamber and a second room in the form of a day-room or a corner annex. Then, a country hut changed into a three-room house. But in the most of cases, there can be observed only one chimney, hence a concentration of kitchen and heat elements in the central part of the building. Such a solution enabled to heat the rooms located by the bonfire. The central arrangement of the rooms around the fire facilities was connected not only to the heat economy in the house, but also to the concentration of a family life by a common home fire, placed in the great room. Concentrated fire facilities, though being extended as far as the culture of people was arising, always fulfilled a postulate of economic usage of fuel and the smallest amount of work to service it. An essential aspect was also the preservation of equilibrium between the heat ability of the fire facilities and inevitable loss of heat through walls, ceiling and door and window openings [8]. The special care both of a constructor and of a user can be noticed here that a chimney system ensured an economical energy management, what definitely characterized houses at that time. An average of traditional stoves was that they cumulated heat and removed an excessive steam.

The folk architecture has been using the building materials which were the most accessible in a given region and with the use of simple tools. Hence, it was organic and because of that it may delight with its perfection, which had been worked out by generations and whose form can be an inspiration for modern creators [3].

Since time immemorial, a wood has been an essential building material in Poland and its application was in a close connection with the degree of forestation of specified regions. The wood is characterized by numerous advantages, but the most important is that it has good heat-protecting features and the buildings made of it ensure the optimal health conditions to their users. In the construction of monolithic wooden walls, predominated a wreath system with various ways of quoining. The joints between separate beams were sealed with a moss, couch or heather, covered with decorated straw plaits, but the most commonly – covered up with clay and limed. A brick came in use relatively lately – only at the beginning of 20th century. In the regions where a clay occurred and was difficult to get a wood, there was used a clay or mixed construction, i.e. a wooden skeleton filled with clay or brick.

As the door and window openings are the elements of a building which lets out relatively much heat, there were attempts in the folk architecture to minimize their area, hence the rooms not always were well illuminated. The windows had generally singular panes, which decreased their thermoinsulating power. However, a special attention should be paid at decorative window shutters, which were being often used – they were closed on a night-time and at some windows, even on a whole winter period. Then they were sealed with straw and opened only at spring. As well, window and door bands protected the house from excessive heat loss, by the way they added a specific charm to an elevation and arranged its whole wall. Their role was mainly to seal frame joints with the wall construction. Both the shutters and the bands themselves were decorated with motives taken from a surrounding world and introduced as the symbols underlining the close connection of a human being with nature.

The adaptation of dwelling houses to climate conditions concerned also the localization of objects at insolated and less windy areas. In the Polish folk architecture, with the exception of mountainous regions, since the longest time there has been avoided to built houses in valleys and terrain hollows.

THE LOW ENERGY-CONSUMING ARCHITECTURAL SOLUTIONS AT THE CHOSEN EXAMPLES OF THE NORTHERN CASUBIA HUTS

The hut form the northern part of Casubia (coastal) is a wide-frontage house without arcades. Apart of that, it is characterized among the others, as follows: two-duct and multi-room system of projection; skeleton walls usually filled with clay or brick; a gable roof with jerkin head and often with a squint window under a roof ridge, inserted in wind beams; the roof with principal rafters ended with decorative finials (so-called 'śparogi'), loosely covered with straw or reed and at exclusively agriculturally poor regions – with heather as well.

The examples of Casubian huts can be two preserved buildings: the one in Karwieńskie Błota, the second – in Nadole.

A dwelling house (in fact, an one-building homestead) in Karwieńskie Błota as well as the whole arrangement of the village (a row swamp village) are the examples of Hauländer architecture and settlement, which actually was not a native Casubian architecture (Photo 1, 2). Small Karwieńskie Błota, located at the road from Krokowa to Karwia, is called by the Casubians "Olędry" (Polish name of Hauländers). This name derives from the Dutch (Polish: "holenderski") settlers, who came there in 16th century and settled in for hundreds of years. The Dutch settlers, similarly to the German, played a significant role, bringing a spandrel construction at the Polish ground – especially developed in the Netherlands. Generally, in that time the spandrel construction characterized the whole North-Eastern Europe – it had arisen mainly due to specific natural conditions, i.e. lack of sufficient amount of wood. A spandrel filled originally with less long-lasting materials, as clay or wood mixed with clay, gravel and straw, was replaced by a much more long-lasting construction, which is a timber framing. In the regional nomenclature, the timber framing is called "Prussian wall" or "brick truss" [4].

A special attention must be paid at the second of the dwelling houses, localized in a historic homestead, representing a type of a traditional village preserved in surroundings of the Żarnowieckie lake (Photo 3, 4). It is the best preserved and the most characteristic agricultural homestead from its period in the northern Casubia.

The surroundings of the Żarnowieckie lake have been for the longest time an attractive settlement region. The specificity of the geographic environment and the isolation of the village imparted pretty typical view to the native economy, till the mid of 19th century strongly connected to an agriculture, breeding of cattle and poultry as well as fishery as sidelines.

The hut constituted a functional arrangement for a three-generation family living there. It was determined by a specificity of rich farmsteads: indivisibles, handed over to successors in current owners' lifetime. The house was built ca. 1846 at a field stone underpinning, it has the walls of the skeleton construction filled with clay at perches as well as the rafter roof with jerkin heads, covered with reed, angled at ca. 48°.

A reed, apart of a straw, was the most common material for roofing. It has many advantages, thanks to which is better than the straw, namely it is longer, more resistant both to damp and drought, it is more watertight as well, hence it can be laid in thicker layers at laths. On the other side, the straw has better thermal features, which consist in keeping favorable temperature in rooms in winter and in summer. Thanks to many advantages, a roof covered by the reed and straw survived a very long time despite many bans and orders of Prussian, and then German and Polish authorities.

The timber frame construction of houses enabled to preserve inside a warm in winters and a smooth cool in summers. Despite of the appearances of keeping damp, in reality this construction was characterized by the dry inside. Some walls of the timber frame construction filled with brick were covered by clay-gravel pugging – in aim to improve the thermal conditions inside the house as well as to protect the wooden elements of the construction. The timber framing was treated as a transitory construction between the wooden and the brick one and in the northern Casubia was a mix of foreign influences and native forms of building technique. Building of walls with filling the free areas of a frame with unfired clay (called "paca") was an imitation of the timber framing construction filled with brick. The usage of "paca" was caused by the lack of local points of a brick production, thus – by too high price of brick.

The hut has a wide frontage, two ducts, is divided by a central chimney, so-called "black kitchen" with heating stoves made of "paca" and fireplaces in the rooms (Figs. 1, 2). This fire facility, as it was mentioned earlier, played the specific role in the house.

Fig. 1. The plan of the ground floor of the hut in Nadole (by Author): 1 – hall, 2 – main room, 3 – corner annex, 4 – chamber, 5 – black kitchen warm zone cold zone

The name "black kitchen" is attributed to the inside of a wide chimney in its lower part, reaching the hut ceiling line. In this inside is placed a kitchen range, adjoining the one of the chimney walls, uncovered or with a closed furnace. The black kitchen was created at the turn of 17th and 18th century after removing an oven from the chimney. It is not known to the majority of the Casubian people, with exception of the peripheral regions adjoining these parts of Casubia inhabited by Germans. The black kitchen, though it is known in the northern Casubia, is loosely connected to the material culture of this region [4]. The entrance to the black kitchen – a chimney shaft, with a wide base – was from a hall. It functionally connected an inlet to heating stoves fed with wood and peat with a smoke and soot offtake from the fireplaces in rooms (Photo 5).

The hut in Nadole represents a two-duct arrangement of a building, dividing the inside into warm and cold zones. It has the 2.2-metre-high rooms. The warm, south-western zone are the rooms used to be occupied by grandparents as well as young owners with children and servants. The main entrance to the building led from a flower garden, through the cobbled hall, to the big main room, where the family life was concentrated. Beyond the main room, in the cold zone of the building, was placed a chamber filled up by tools connected with processing and storage of food. An opposite, smaller part of the hut was occupied by grandparents. A corner annex with a small window in the cold zone served as a sleeping room as well as a storeroom for a more precious clothes and personal things.

Windows in a building were small, with single panes. An arrangement of windows is connected to a lighting of the hut inside. Simultaneously, a special attention should be paid to the fact that the magnitude of the windows was adapted to the expected temperature of a room. The greatest windows were in the warm zone rooms, smaller – in the corner annex, the smallest – in the chamber and the cold zone hall. A four-pane window frame in a small window had generally 0.65 to 1 m of width and 0.6 to 1 m of height. In the corner annexes, as a rule, were only two panes, arranged vertically. In rich peoples' houses till the beginning of 19th century and in poor peoples' huts almost till the end of 19th century, the windows played a role of a light source, but they did not controlled a fresh air flow into the house inside. As the mobile casements had been introduced thanks to hinges, a need arose to strengthen the windows more durably in the walls with the use of break jambs, what also contributed to the decrease of heat losses from the building. An integral part of the windows in the Casubian huts from 19th century were shutters, whose task, apart of the protection from thieves, was first of all the protection from an excessive overchilling of the hut inside. The shutters were used to be placed in greater windows, but they did not covered small windows with one casement.

An attic of a dwelling house as the place for storage of cereals was a good isolator of the ground floor. There was also used to be stored a dismounted weaving workshop and every tools serving to a flax treatment and to a flax thread production. In winter, there also stood a box with meat.

The whole homestead in Nadole is made up with the dwelling house, the farm buildings, accompanying objects as well, cellar, coach house, dovecot and apiary, arranged in the settlement according to the manner strictly determined by their functions and regulations (Fig. 3). The buildings are arranged on a tetragon plan: a barn parallel to a road with the possibility of entry from both sides – the road and the farmyard. Before the gate, at the farmyard side, was a treadmill. At the right side of the entry road, perpendicularly to the road, is placed a cowshed with a corral for animals and a cobbled dunghill. To the left side of the cowshed, the coach house is adjoined and they both are joined with a common roof. The hut, founded in the back of the farmyard, separated from the farm part with the flower garden, partly turned to a lake, constitutes the representative and at the same time snug element of the farmyard. In its closest neighborhood is the cellar, well and vegetable garden. In an orchard were placed an oven and an apiary.

The most of Casubian villages was arranged in such way that there existed a great possibility to locate a dwelling house toward the sun, what definitely affected a heat management in a house. Simultaneously, the localization of a flower garden did not overshadowed a south house elevation. It must be reminded that in the moderate Polish climate, the deviation of 25° do not affect yet noticeably the amount of sun energy being delivered to the house [5]. According to another sources, the deviation from the preferred angle should not exceed 15 ÷ 20° [1,6]. In the case of the hut in Nadole, the deviation from the N-S axis toward west is equal ca. 35°.

To sum up, the functional and spatial elements affecting the heat saving in the folk architecture, basing on the example of the Casubian huts, are mainly:

• a condensed building mass on a square plan,

• a big roof, with appropriately angled (48°) roof slopes and eaves protruding beyond external walls up to 70 cm as well as a roofing material with good thermoinsulating features – reed,

• a small height of rooms – ca. 2.2 m,

• a hall, protecting a house inside from wind and cold air flow,

• a two-duct arrangement, dividing the house into a cold and warm zone,

• one chimney, what spells a concentration of kitchen and heating facilities in the central part of the house,

• the application of a building material with good warm-protecting features (wood and clay at perches),

• window openings with limited areas and shutters,

• the location of the dwelling house toward the  sun (a deviation from the N-S axis toward west is equal ca. 35°).

The analysis of the individual elements of the folk architecture showed its astonishing and well-thought-out appropriateness – from the rooms arrangement to shaping the building mass itself – which proves that the society of that time was being used all available means that their houses lost as small amount of heat as it is possible. For sure, in many cases these objects can serve as an example of a low energy-consuming architecture for today's Polish country house designers [3].

CONCLUSIONS

During construction of today's country houses, it is worth to refer to the tradition. An inspiration can be not only more and more often appreciated beauty of former residences, but also the solutions serving to heat protection, worked out by our ancestors.

The old folk architecture, which is a result of the work of numerous generations, should become a pattern and inspiration in quest of low energy-consuming solutions by designing of new country dwelling houses. Of course, it should be remembered that an attachment to the tradition cannot brake the technical progress. There must be taken into consideration the contemporary life conditions, building regulations, including fire regulations as well as e.g. wood shortage. A multitude of building materials available at the market and modern energy efficient technologies should be joined to the adaptation of newly built dwelling houses to regional traditions.

The common characteristic features of a traditional folk hut and a modern house built according to the rules of a low energy-consuming architecture can include:

• a condensed building mass usually on a rectangular plan,

• a gable or hipped roof with an attic playing a role of thermal buffer,

• a kitchen localized in the middle of the house, which enables a steady heat distribution and supports a natural ventilation,

• a division into a cold and warm zone,

• wide eaves protecting from an excessive sun and precipitations,

• windows with shutters.

It is worthy of attention that the forms of regional buildings show with an astonishing consequence the spatial scheme used in the today's energy efficiency architecture. He fundamental difference, of course apart of the technical progress, consists in a material and constructive solution of walls. The method of their construction in historical houses depended on the availability of a building material in a given region, but independent on the exposition to the sun. In the low energy-consuming houses presently being carried out the south walls are being designed in another way than the north ones. The former country houses saved warm not only due to their appropriate location and simple architecture, but also to a small window area. Nowadays, there is not such limitations. It is possible to accomplish the houses which are both energy efficiency, optimally glazed and opened to environment.

The problem of a building heat protection has always existed but there are changing the technical means of its solving. It seems that the part of the rules worked out in the past, mainly through an empirical solving the problems, should be also applied today. An example can be i.a. application of a heating shaft, which connects smoke or exhausting flues with a fireplace and accumulating mass, e.g. made of a local stone. This solution could contribute mainly to increase a heat accumulation.

The culmination of a quest the most possible effectiveness of residences being constructed, dependent on respect for energy, is so-called low energy-consuming architecture, which is a synthesis of the best solutions worked out during centuries.

REFERENCES

1. Celadyn W., 2004. Przegrody przeszklone w architekturze energooszczędnej [Glazed baffles in energy efficiency architecture]. Wydawnictwo Politechniki Krakowskiej, Kraków [in Polish].

2. Ciołek G., 1947. Podstawy regionalnego planowania wiejskiego [Rudiments of regional country planning]. Wydawnictwo Architektura, 2, 46-51 [in Polish].

3. Górecka M., 2004. Architektura energooszczędnego domu mieszkalnego polskiej wsi w aspekcie zrównoważonego rozwoju [Energy efficient dwelling house architecture from the point of view of the balanced development]. Oficyna Wydawnicza Politechniki Warszawskiej, Warszawa [in Polish].

4. Knyba J., 1987. Budownictwo ludowe na Kaszubach [Folk architecture on Casubia]. Wydawnictwo Morskie, Gdańsk [in Polish].

5. Kotarska K., Kotarski Z., 1989. Ogrzewanie energią słoneczną (systemy pasywne) [Solar energy heating (passive systems)]. NOT-SIGMA, Warszawa [in Polish].

6. Laskowski L., 2005. Ochrona cieplna i charakterystyka budynku [Heat protection and building characteristics]. Oficyna Wydawnicza Politechniki Warszawskiej, Warszawa [in Polish].

7. Piaścik F., Tłoczek I. F., 1961. Budownictwo mieszkaniowe na wsi. Dom jednorodzinny [Country housing. Single family house]. Wydawnictwo Politechniki Warszawskiej, Warszawa [in Polish].

8. Tłoczek I. F., 1985. Dom mieszkalny na polskiej wsi [Dwelling house on the polish country]. PWN, Warszawa [in Polish].

9. Wieczorkiewicz W., 1988. Budynek mieszkalny na wsi [Country dwelling house]. Arkady, Warszawa [in Polish].

Accepted for print: 2.10.2008

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.