In this article John Bates Clark introduces explicitly the concept of marginal labour value and gives it an interpretation based on a technical production function. This is an improvement of Gossen's and Jevon's hedonistic interpretation of labour. But he did not provide a mathematical presentation of the notion of marginal labour as the reciprocal of the marginal productivity of labour. The article has been published again in 1896 in a slightly modified form as "The Unit of Wealth" in Festgaben für Karl Knies zur fünfundsiebzigsten Wiederkehr seines Geburtstages in dankbarer Verehrung dargebracht von Eugen v. Böhm-Bawerk ... O. v. Boenigk ... J. B. Clark ... Berlin: O. Haering, 1896; edited by Otto Johannes Eugen Ferdinand Wilhelm (Freiherr von) Boenigk. This book includes also Böhm-Bawerk's article "Zum Abschluss des Marxschen Systems" ("Karl Marx and the Close of His System"). There is another publication with the same title: Clark, John B. 1893. The Ultimate Standard of Value. Publications of the American Economic Association 8, no. 1: 82-87, which concentrates on the main points of the argument.
