book. The buying and selling of human work effort can and has taken many more different forms than Marx acknowledges—especially in the area of services. A modern information society makes possible all kinds of new forms of hustling. Marx said himself that "Above all [capitalism] overturns all the legal or traditional barriers that would prevent it from buying this or that kind of labour-power as it sees fit, or from appropriating this or that kind of labour". The concept of the value of labour power referred to the underlying economic relationship, not to be confused with the formalities of all the kinds of labour contracts which are possible. See also Abstract labour and concrete labour Compensation of employees Reserve army of labour Surplus labour Surplus product Wage labour Notes References Samuel Bowles & Herbert Gintis, "The Problem with Human Capital Theory—A Marxian Critique", American Economic Review, vol. 65(2), pages 74–82, (1975) Tom Brass, Towards a Comparative Political Economy of Unfree Labour: Case Studies and Debates. (Frank Cass, London, 1999). Tom Brass and Marcel Van Der Linden (eds.), Free and Unfree Labour: The Debate Continues (International and Comparative Social History, 5). New York: Peter Lang AG, 1997. Harry Braverman, Labor and Monopoly Capital: The Degradation of Work in the Twentieth Century. New York: Monthly Review Press, 1974. The Critical Lawyer's Handbookm Ben Fine, Labour Market Theory: A Constructive Reassessment. Routledge, London, 1998. Bonnie Fox, Hidden in the Household: Women's Domestic Labour Under Capitalism, Women's Press, 1980. Ian Gough & Leslie Doyal, A Theory of Human Need, Macmillan Press Ltd. 1991. Ian Gough, Global Capital, Human Needs and Social Policies: Selected Essays 1994-99 London: Palgrave, 2000. Geoffrey Hodgson, Capitalism, Value and Exploitation (Martin Robertson, Oxford, 1982). Makoto Itoh, The Basic Theory of Capitalism: The Forms and Substance of the Capitalist Economy. Barnes & Noble, 1988. Kenneth Lapides, Marx's Wage Theory in Historical Perspective: Its Origins, Development, and Interpretation. Westport: Praeger 1998. Marcel van der Linden, The Workers and the World; Essays toward a Global Labour History. Leiden: Brill, 2008. Ernest Mandel, The Formation of the Economic Thought of Karl Marx. Monthly Review Press, 1969. Karl Marx, Das Kapital, Volume 1. Roman Rosdolsky, The Making of Marx's "Capital". London: Pluto Press, 1977. Bob Rowthorn, "Marx's Theory of Wages", a chapter in Bob Rowthorn, Capitalism, Conflict, and Inflation, Lawrence & Wishart, London. Ian Steedman, "Marx on Ricardo", in: Ian Bradley and Michael Howard (eds),