From Citizendium, the Citizens' Compendium
Coal mining is a term that encompasses the various methods used to extract the carbon-containing rock called coal from the ground. Coal tends to exist in seams, which are lateral layers under the earth that may vary in depth from one or two feet to dozens of feet.
Coal mining methods
Mining of coal seams is achieved in several different ways. "Strip" mines scrape coal from the earth's surface; they may be large open pits, or if on a mountain, result in ribbons chewed away from around the perimeter of a mountain at each level where a seam of coal exists. So-called "drift" mines angle horizontally into a mountainside and may be very shallow (i.e., not tall enough for a person to stand up in). "Shaft" mines, also called deep mines, reach down vertically to open into person-sized horizontal tunnels which may be miles from the surface.
Strip mines remove any top soil with bulldozers to get at coal near the earth's surface. Coal is excavated from the ground in what becomes large pits, or else ribbons of stripped land stretch around a mountain. After strip mining has exhausted the available surface coal, the mining company often abandons the site with no restoration, leading to severe erosion problems (with resultant flooding or pollution) and to an unsightly landscape that cannot support plant growth due to the lack of topsoil. Drift mines may be used after strip mining has used up surface coal. Because drift mines tend to be shallow, special equipment may be required to mine them, on which, for example, workers can lie flat on short vehicles moving inside the tunnel. Drift mining is common in the extreme southwest corner of Virginia. Deep mines are similar to those for any other mineral deposit found deep enough in the earth that the cost of removing the overburden is prohibitive. Shafts are dug and veins of coal are excavated and transported to the surface.
Deep and drift mining safety
Early mining methods led to very unsafe mines which often were not even represented on maps at all, or were represented inaccurately. Early mining methods led to irregularly spaced supporting pillars, which often were not represented on maps, or were represented inaccurately. Modern mines have regular pillars at safe intervals of known thickness.
Even using the best known methods, underground coal mining is hazardous work. In addition to the hazard of simple cave-ins, miners have to worry about their tunnels flooding, accumulation of "bad air" (gases lacking enough oxygen), accumulation of explosive gases resulting in fires and/or cave-ins, and many other unexpected problems. Bad air and water can suddenly flood a tunnel if a pocket of the non-oxygenated gas or water is reached without warning when removing coal from a seam.
Following known best practices can reduce the likelihood of extensive loss of life during catastrophic mining accidents. Poor safety records of some mine owners led to the formation of labor unions around the world, and today there remains a high degree of solidarity among mine workers. Mining deaths still occur periodically that arguably could have been prevented with appropriate safety equipment, training and safety procedures.
History of coal mining
Coal has been used for centuries for small-scale furnaces. Around 1800 it became the main energy source for the Industrial Revolution, the expanding railway system of countries being a prime user. Britain developed the main techniques of underground mining from the late 18th century onward with further progress being driven by 19th and early 20th century progress.
By 1900 the United States and Britain were the chief producers, followed by Germany.
However oil became an alternative fuel after 1920 (as did natural gas after 1980). By the mid 20th century coal was for the most part replaced in domestic as well as industrial and transportation usage by oil, natural gas or electricity produced from oil, gas, nuclear or water power.
Since 1890 coal has also been a political and social issue. Coal miners' labor unions became powerful in many countries in the 20th century. Often, the miners were leaders of the left or Socialist movements (as in Britain, Germany, Poland, Japan, Canada and the U.S.). Since 1970, environmental issues have been paramount, including the health of miners, destruction of the landscape from strip mines and mountaintop removal mining, air pollution, and contribution to global warming. Coal remains the cheapest energy source by a factor of 50% and even in many economies (such as the U.S.) it is the primary fuel used in electricity generation.
Coal was first used as a fuel in various parts of the world during the Bronze Age, 2000-1000 BCE. The Chinese began to use coal for heating and smelting in the Warring States Period (475-221 BCE). They are credited with organizing production and consumption to the extent that by the year 1000 CE this activity could be called an industry. China remained the world's largest producer and consumer of coal until the 18th century. Roman historians describe coal as a heating source in Britannia.
The earliest uses of coal in the Americas were by the Aztecs, who used coal not only for heat and as ornaments as well. Coal deposits near the surface were extracted by colonists in Virginia and Pennsylvania in the 18th century. Early coal extraction was small-scale, the coal lying either on the surface, or very close to it. Typical methods for extraction included drift mining and bell pits. In Britain, some of the earliest drift mines (in the Forest of Dean) date from the medieval period.
Small scale shaft mining as well as drift mines were the most common forms used prior to mechanization that occurred in the twentieth century. This took the form of a "bell pit", the extraction working outward from a central shaft, or a technique called "room and pillar" in which "rooms" of coal were extracted with pillars left to support the roofs. Both of these techniques, however, left considerable amount of usable coal behind.
The Industrial Revolution
From its origins in Britain after 1750, the world-wide industrial revolution has been dependent upon the availability of coal to power steam engines and industrial equipment of all kinds. International trade expanded exponentially when coal-fed steam engines were built for the railways and steamships in the 1810-1840 era. Coal was cheaper and much more efficient than wood in most steam engines. As central and northern England contains an abundance of coal, many mines were situated in these areas. The small-scale techniques were unsuited to the increasing demand, with extraction moving away from surface extraction to deep shaft mining as the Industrial Revolution progressed.
The large-scale exploitation of coal was an important moving force behind the Industrial Revolution. Coal was used in making iron and steel. It was also used to power the early railroad locomotives and steamboats, driven by coal-burning steam engines, which made possible the transport of very of large quantities of raw materials and manufactured goods. Coal-burning steam engines also powered many types of factory machinery.
The largest economic impacts of exploiting coal during the Industrial Revolution were experienced in Wales and the Midlands of England, and in the Rhine and Ruhr river areas of Germany. The early railroads also played a major role in the westward expansion of the United States during the 19th century.
Deep shaft mining in Britain started in the late 18th century, although rapid expansion occurred throughout the 19th and early 20th centuries. The location of the coalfields helped to make the prosperity of Lancashire, of Yorkshire, and of South Wales; the Yorkshire pits which supplied Sheffield were only about 300 feet deep. Northumberland and Durham were the leading coal producers and they were the sites of the first deep pits. In much of Britain coal was worked from drifts, or scraped off when it outcropped. Small groups of part-time miners used shovels and primitive equipment. Before 1800 a great deal of coal was left in places as support pillars. As a result, in the deep Tyneside pits (300 to 1,000 ft. deep) only about 40 percent of the coal could be extracted. The use of wood props to support the roof was an innovation first introduced about 1800. The critical factor was circulation of air and control of explosive gases. At first fires were burned to create air currents.
Coal was so abundant in Britain that the supply could be stepped up to meet the rapidly rising demand. About 1770-1780 the annual output of coal in was some 6.3 million tons (or about the output of a week and a half in the twentieth century). After 1790 output soared, reaching 16 million tons by 1815. The miners, less menaced by imported labor or machines than were the cotton operatives, had begun to form unions and fight to control wages and working conditions against the coal owners and royalty-lessees.
Technological development throughout the 19th and 20th century helped both to improve the safety of colliers and the productive capacity of collieries they worked in. Scott examines the importance of path dependence effects in impeding the diffusion of high throughput mechanized mining systems in the British coal industry. Evidence shows that the industry had become "locked in" to low throughput underground haulage technology because of institutional interrelatedness between Britain's traditional practice of extensive in-seam mining and its unique system of fragmented, privately owned mineral royalties. Fragmented royalties prevented the concentration of workings and introduction of high throughput main haulage systems that underpinned the rapid productivity growth of European producers. Meanwhile, technical interrelatedness between the haulage systems taking coal to the pit shaft and operations further "upstream" created bottlenecks that both slowed the overall rate of mechanization and limited the productivity gains from the mechanization that did occur.
In the late 20th century, improved integration of coal extraction with bulk industries such as electrical generation helped coal maintain its position despite the emergence of alternative energies supplies such as oil, natural gas, and, from the late 1950s, nuclear power used for electricity. More recently coal has faced competition from renewable energy sources and biofuels.
However, the 1980s and 1990s saw much much change in the coal industry within the UK, with the industry contracting, in some areas quite drastically. Many pits were 'uneconomic' to work at current wage rates compared to 'cheap' North Sea oil and gas, and in comparison to subsidy levels in Europe. The Miners' Strike of 1984 and subsequent strikes helped shrink the industry . The National Coal Board (by then British Coal), was privatized by selling off a large number of pits to private concerns through the mid 1990s.
Pretty profiles Welsh mining labor leader David Morgan (1840-1900) and explores the dynamics of labor relations in the Welsh coal mining industry during 1851-1901. First elected to the executive committee of the Amalgamated Association of Miners (AAM) in 1872, Morgan was active in numerous strikes for better wages, working conditions, and hours. His role in the arbitration of an 1875 labor dispute won him respect both from his fellow miners and from mine owners. With the demise of the AAM that same year, Morgan turned his attention to working-class politics. Although often at odds with fellow miners and unions, Morgan maintained his popularity in the community, taking a seat on the Aberdare school board in 1883. At the same time Morgan acted as the miners' agent for the Aberdare, Methyr, and Dowlais Miners' Associations. During the 1890's, Morgan attempted to forge a peace between rival trade unions, but continuing animosity with mine owners caused his arrest and eventually his loss of influence over Welsh miners.
Coal became a political issue, as the miners formed the National Union of Mineworkers, in 1888, which claimed 600,000 members in 1908. Much of the 'old left' of British politics can trace its origins to coal-mining areas. The failed General Strike of 1926 was led by the miners. The Labor government in 1947 nationalized coal into the National Coal Board, giving miners access to control of the mines via their control of the Labor party and the government.
Health and safety
McIvor and Johnston (2005) analyze the gap between knowledge of occupational lung diseases and actions by industry officials and workers to limit their exposure to the life-threatening conditions in British coal mining and asbestos work during the 20th century. Although respiratory diseases had been medically documented in the 19th century, it was not until the 1910s that research institutions such as the Industrial Fatigue and Industrial Health research boards were formed to offer recommendations for occupational health. Workplace regulation of some asbestos work began in 1931. Legislation regarding disability payments for coal miners was not enacted until 1943. Many miners and asbestos workers were reluctant to implement the use of safety gear as an assertion of manliness, despite increasingly recognized health concerns and regulatory efforts throughout the mid-20th century to improve workplace conditions. When legislation was first introduced to protect workers from silicosis (1919), coal mining was not a serious target of the regulation. By the late 1920's, scientific investigation had determined that coal mining could create a silicosis threat. The South Wales Miners' Federation fought individual compensation cases in the 1920's and in the 1930's lobbied civil servants and legislators. By the late 1930's, the Medical Research Council recognized increased claims of coal miners, and its report in 1945 provided a significant reappraisal of respiratory diseases among coal miners and colliery workers. Bufton and Melling reconsiders the class-based argument versus the perspective that bureaucrats and policymakers were making conscientious attempts to achieve consensus solutions to the complex issue of respiratory health problems. During the interwar years, the problems of individual miners became part of a broader political and intellectual struggle over the responsibility for workplace health.
In spite of significant improvements in occupational health and safety standards in Scottish coalfields during the 20th century, the underground working environment remained dangerous until the coal industry's ultimate demise. There was a gap between state and employer action to improve safety and health in the pits, which largely explains this dangerous continuity. The coal industry's nationalization in 1947, which brought Great Britain's small privately owned pits under the new National Coal Board's (NCB) control, ushered in concern for miners' health and safety. Despite the NCB's efforts, however, safety underground had increased little by 1962 due to cost cutting and an intense productivity drive in the industry, resulting in a greater occurrence of the disease pneumoconiosis, caused by inhaling coal dust. In 1947 the NCB began implementing dust suppression measures, such as fitting coal-cutting machinery with water sprays and issuing masks. While the mines inspectors' reports note the miners' reluctance to wear the masks, the oral evidence suggests that the miners rejected them because they were just a piece of gauze. The oral testimony is especially enlightening when it comes to ascertaining the personal impact of coal miners' lung diseases and disability, which included an erosion of their sense of masculinity.
Anthracite (or "hard" coal), clean and smokeless, became the preferred fuel in cities, replacing wood by about 1850. Anthracite from the Northeastern Pennsylvania coal region (and later from West Virginia) was typically used for household uses because it is of high quality, with few impurities, and stoves and furnaces were designed for it. The rich Pennsylvania anthracite fields were close to the eastern cities, and a few major railroads like the Reading Railroad controlled the anthracite fields. By 1840, hard coal output had passed the million short ton mark, and then quadrupled by 1850.
Bituminous (or "soft coal") mining came later. In the mid-century, Pittsburgh was the principal market. After 1850, soft coal, which is cheaper but dirtier, came into demand for railway locomotives and stationary steam engines, and was used to make coke for steel after 1870. Total coal output soared until 1918; before 1890, it doubled every ten years, going from 8.4 million short tons in 1850 to 40 million in 1870, 270 million in 1900, and peaking at 680 million short tons in 1918. New soft coal fields opened in Ohio, Indiana and Illinois, as well as West Virginia, Kentucky and Alabama. The Great Depression of the 1930s lowered the demand to 360 million short tons in 1932.
The United Mine Workers (UMW), formed in the 1880s in the Midwest, was successful in its strike against bituminous mines in the Midwest in 1900. However, the union's strike against the anthracite mines of Pennsylvania turned into a national political crisis in 1902. President Theodore Roosevelt brokered a compromise solution that kept the flow of coal going, and won higher wages and shorter hours for the miners, but did not include recognition of the union as a bargaining agent.
Under the leadership of John L. Lewis the UMW became the dominant force in the coal fields in the 1930s and 1940s, producing high wages and benefits. Repeated strikes caused the public to switch away from anthracite for home heating after 1945, and that sector collapsed.
In 1914 at the peak there were 180,000 anthracite miners; by 1970 only 6,000 remained. At the same time steam engines were phased out in railways and factories, and bituminous was used primarily for the generation of electricity. Employment in bituminous peaked at 705,000 men in 1923, falling to 140,000 by 1970 and 70,000 in 2003. Environmental restrictions on high-sulfur coal, and the rise of very large-scale strip mining in the west (especially the Powder River fields in Wyoming and adjacent states), caused the sharp decline in underground mining after 1970. UMW membership among active miners fell from 160,000 in 1980 to only 16,000 in 2005, as non-union miners predominated. The American share of world coal production remained steady at about 20% from 1980 to 2005.
Canada had a small coal industry concentrated at Cape Breton in Nova Scotia. At its peak in 1949 25,000 miners dug 17 million metric tons of coal from mines. The miners, who lived in company towns, were politically active in left-wing politics. All the mines were closed by 2001. The United States always supplied the coal for the industrial regions of Ontario. By 2000 about 19% of Canada's energy was supplied by coal, chiefly imported from the U.S.
Germany: The Ruhr Basin
The first important mines appeared in the 1750s, In 1782 the Krupp family began operations near Essen. After 1815 entrepreneurs in the Ruhr Area, which then became part of Prussia took advantage of the tariff zone (Zollverein) to open new mines and associated iron smelters. New railroads were built by British engineers around 1850. Numerous small industrial centers sprang up, focused on ironworks, using local coal. The iron and steel works typically bought mines, and erected coking ovens to supply their own requirements in coke and gas. These integrated coal-iron firms ("Huettenzechen") became numerous after 1854; after 1900 they became mixed firms called "Konzern".
The average output of a mine in the Ruhr Area in 1850 was about 8,500 short tons and it employed about 64 miners. By 1900, the average mine's output had risen to 280,000 short tons and the employment to about 1,400. Total Ruhr coal output rose from 2.0 million short tons in 1850 to 22 million in 1880, 60 million in 1900, and 114 million in 1913, on the verge of war. In 1932 output was down to 73 million short tons, growing to 130 million in 1940. Output peaked in 1957 (at 123 million), declining to 78 million short tons in 1974.
By 1830 when iron and later steel became important the Belgium coal industry had long been established, and used steam-engines for pumping. The Belgian coalfield lay near the navigable River Meuse, so coal was shipped downstream to the ports and cities of the Rhine-Meuse delta. The opening of the Saint-Quentin canal allowed coal to go by barge to Paris. The Belgian coalfield outcrops over most of its area, and the highly folded nature of the seams meant that surface occurrences of the coal were very abundant. Deep mines were not required at first so there were a large number of small operations. There was a complex legal system for concessions, often multiple layers had different owners. Entrepreneurs started going deeper and deeper (thanks to the good pumping system). In 1790, the maximum depth of mines was 220 meters. By 1856, the average depth in the area west of Mons was 361, and in 1866, 437 meters and some pits had reached down 700 and 900 meters; one was 1,065 meters deep, probably the deepest coal mine in Europe at this time. Gas explosions were a serious problem, and Belgium had high fatality rates. By the late 19th century the seams were becoming exhausted and the steel industry was importing some coal from the Ruhr.
Post World War II Europe
After World War II much of Europe's coal mines passed into effective government control, with the British coal mines being nationalized under the control of the National Coal Board. The plan to nationalize the coal mines had been accepted in principle by owners and miners alike before the elections of 1945. The owners were paid £165,000,000. The government set up the National Coal Board to manage the coal mines; and it loaned it £150,000,000 to modernize the system. The general condition of the coal industry has been unsatisfactory for many years, with poor productivity. In 1945 there were 28% more workers in the coal mines than in 1890, but the annual output was only 8% greater. Young people avoided the pits; between 1931 and 1945 the percentage of miners more than 40 years old rose from 35% to 43%, and 24,000 over 65 years old. The number of surface workers decreased between 1938 and 1945 by only 3,200, but in that same time the number of underground workers declined by 69,600, substantially altering the balance of labor in the mines. That accidents, breakdowns, and repairs in the mines were nearly twice as costly in terms of production in 1945 as they had been in 1939 was probably a by-product of the war. Output in 1946 averaged 3,300,000 tons weekly. By summer 1946 it was clear that the country was facing a coal shortage for the upcoming winter with stock piles 5 million tons too low. Nationalization exposed both a lack of preparation for public ownership and a failure to stabilize the industry in advance of the change. Also lacking were any significant incentives to maintain or increase coal production to meet demand.
In Eastern Europe, the Communist governments nationalized all the mines after 1945.
Co-operation on coal trading was the impetus for forming the "European Coal and Steel Community" (ECSC) in 1951. Integrationists like French foreign minister Robert Schuman realized that coordinating the coal and steel markets of Germany, France, Italy and the Low Countries could lead to "spillover" in other policy areas; the ECSC indeed morphed into the EEC and European Union.
Coal produces over 80% of China's energy; 2.3 billion metric tons of coal were mined in 2007. Despite the health risks posed by severe air pollution in cities (see Beijing) and international pressure to reduce greenhouse emissions, China’s coal consumption is projected to increase in line with its rapid economic growth. Most of the coal is mined in the western provinces of Shaanxi and Shanxi and the northwestern region of Inner Mongolia. However most coal customers are located in the industrialized southeastern and central coastal provinces, so coal must be hauled long distances on China’s vast but overextended rail network. More than 40% of rail capacity is devoted to moving coal, and the country has been investing heavily in new lines and cargo-handling facilities in an attempt to keep up with demand. Despite these efforts, China has suffered persistent power shortages in industrial centers for more than five years as electricity output failed to meet demand from a booming economy. Demand for electricity increased 14% in 2007.
Mining has always been dangerous, because of explosions, cave-ins, methane gas and the difficulties of timely underground rescue. The worst single disaster in British coal mining history was at Senghenydd in South Wales. On the morning of 14 October 1913 an explosion and subsequent fire killed 436 men and boys. Only 72 bodies were recovered. The Monongah Mine disaster in West Virginia (December 6, 1907) was the worst mining disaster in American history. The explosion was caused by the ignition of methane (also called "black damp"), which ignited the coal dust. In all, the lives of an estimated 362 men and boys were lost in the underground explosion. (The actual number of those killed is unknown since records of those entering the mine were not maintained carefully.)
- ↑ Children in coal-mining areas sometimes can't resist entering old mines, which can be especially dangerous.
- ↑ 2.0 2.1 2.2 2.3 Barbara Freese (2003). Coal: A Human History, 1st Edition. Perseus Publishing. ISBN 0-7382-0400-5.
- ↑ Geoff Eley (2002). Forging Democracy:The History of the Left in Europe, 1858 - 2000. Oxford University Press. ISBN 0-19-503784-7.
- ↑ Frederick Meyers (1961). European Coal Mining Unions: Structure and Function. University of California. p.86
- ↑ Nimura Kazuo, Andrew Gordon and Terry Boardman (1998). The Ashio Riot: A Social History of Mining in Japan. Duke University Press. ISBN 0-8223-2018-5. p.48
- ↑ Hajo Holborn (1959). History of Modern Germany. A.A. Knopf. p. 521
- ↑ David Frank (1999). J. B. McLachlan: A Biography: The Story of a Legendary Labour Leader and the Cape Breton Coal Miner. James Lorimer and Company. ISBN 1-55028-677-3. p. 69
- ↑ David Montgomery (1991). The Fall of the House of Labor: The Workplace, the State, and American Labor Activism, 1865-1925. Cambridge University Press. ISBN 0-521-22579-5. p. 343
- ↑ Elspeth Thomson (2003). The Chinese Coal Industry: An Economic History, 1st Edition. RoutledgeCurzon. ISBN 0-7007-1727-7. p. 8
- ↑ Michael Flinn, John Hatcher, David Stoker, Roy Church, Barry Supple and William Ashworth (1984). The History of the British Coal Industry: 1780-1830, the Industrial Revolution (vol.2). Oxford University Press. ISBN 0-19-828283-4.
- ↑ J. Steven Watson (1960). The Reign of George III (vol.12). Clarendon Press. ISBN 0-10-821713-7. p. 516
- ↑ Peter Scott (January 2006). "Path Dependence, Fragmented Property Rights and the Slow Diffusion of High Throughput Technologies in Inter-war British Coal Mining". Business History 48 (1): 20-42. ISSN 1743-7938.
- ↑ 13.0 13.1 Ben Fine (1990). The Coal Question: Political Economy and Industrial Change from the Nineteenth Century to the Present Day. Routledge. ISBN 0-415-04384-0.
- ↑ Catherine Mitchell and Bridget Woodman (2004). The Burning Question: Is the UK on Course for a Low Carbon Economy. Institute for Public Policy Research. ISBN 1-86030-255-6.
- ↑ David A. Pretty (2001). "David Morgan ("Dai O'r Nant"), Miners' Agent: a Portrait of Leadership in the South Wales Coalfield". Welsh History Review 20 (3): 495-531. ISSN 0043-2431.
- ↑ Arthur McIvor and Ronald Johnston (2005). "Medical Knowledge and the Worker: Occupational Lung Diseases in the United Kingdom, 1920-1975". Labor 2 (4): 63-86. ISSN 1547-6715.
- ↑ Mark W. Bufton and Joseph Melling (2005). "'A Mere Matter of Rock': Organized Labour, Scientific Evidence and British Government Schemes for Compensation of Silicosis and Pneumoconiosis among Coalminers, 1926-1940". Medical History 49 (2): 155-178. ISSN 0025-7273.
- ↑ Arthur McIvor and Ronald Johnston (2002). "Voices from the Pits: Health and Safety in Scottish Coal Mining since 1945". Scottish Economic and Social History 22 (2): 111-133. ISSN 0269-5030. Based on interviews conducted with twenty miners who labored in the Lanarkshire, Ayrshire, and Fifeshire coalfields in the years 1945-80, plus documentary evidence
- ↑ Frederick M. Binder (1974). Coal Age Empire: Pennsylvania Coal and its Utilization to 1860. Pennsylvania Historical and Museum Commission. ISBN 0-911124-75-6.
- ↑ Sam H. Schurr and Bruce C. Netschert (1960). Energy in the American Economy, 1850-1975: An Economic Study of Its History and Prospects. Resources for the Future ans John Hopkins Press, pp 60-62.
- ↑ Melvyn Dubofsky and Warren Van Tine (1986). John L. Lewis: A Biography, Abridged Edition. University of Illinois Press. ISBN 0-252-01349-2.
- ↑ Norman J. G. Pounds (1985). An Historical Geography of Europe, 1800-1914. Cambridge University Press. ISBN 0-521-26574-6.
- ↑ Norman J. G. Pounds and William N. Parker (1957). Coal and Steel in Western Europe; the Influence of Resources and Techniques on Production. Indiana University Press. Full text online
- ↑ Mark Tookey (2001). "Three's a Crowd? Government, Owners, and Workers During the Nationalization of the British Coalmining Industry 1945-47". Twentieth Century British History 12 (4): 486-510. ISSN 0955-2359.
- ↑ J. Gillingham (2005). Coal, steel, and the rebirth of Europe, 1945-1955: The Germans and French from Ruhr Conflict to Economic Community. Cambridge University Press. ISBN 0-521-52430-X.
- ↑ Derek W. Urwin (1991). The Community of Europe: A History of European Integration since 1945. Longman. ISBN 0-582-04531-2.