Freedman, R., & Schwartz, H. (1961). Marx on Economics. Harmondsworth: Penguin Books.
Lua i Stíl Chicago (17ú heag.)Freedman, Robert, agus Harry Schwartz. Marx on Economics. Harmondsworth: Penguin Books, 1961.
Lua MLA (8ú heag.)Freedman, Robert, agus Harry Schwartz. Marx on Economics. Harmondsworth: Penguin Books, 1961.
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