"The initial usage of the term "capitalism" in its modern sense has been attributed to Louis Blanc in 1850 ("What I call 'capitalism' that is to say the appropriation of capital by some to the exclusion of others") and Pierre-Joseph Proudhon in 1861 ("Economic and social regime in which capital, the source of income, does not generally belong to those who make it work through their labour").[22]:237 Karl Marx and Friedrich Engels referred to the "capitalistic system"[29][30] and to the "capitalist mode of production" in Capital (1867).[31] The use of the word "capitalism" in reference to an economic system appears twice in Volume I of Capital, p. 124 (German edition) and in Theories of Surplus Value, tome II, p. 493 (German edition). Marx did not extensively use the form capitalism, but instead those of capitalist and capitalist mode of production, which appear more than 2,600 times in the trilogy The Capital."