Theorien über den Mehrwert
The form of value is also mentioned in Marx's 1859 book "A Contribution to the Critique of Political Economy". It is clearly evident in his manuscript of "Theories of Surplus Value" (1861–63). In correspondence with Friedrich Engels in June 1867, Marx provided a first outline of his text on the form of value. Marx first explicitly described the concept in an appendix to the first (1867) edition of Capital, Volume I, but this appendix was dropped in a second edition, where the first chapter was rewritten (rather hurriedly) to include a special section on the form of value at the end.