"For this reason, entrepreneurial activity is just as necessary a factor in the production of goods as technical labor services." > Menger, Carl. (1981) Principles of Economics. > Translated by James Dingwall and Bert Hoselitz. New York: New York University Press. But Menger also wrote: " Entrepreneurial activity must definitely be counted as a category of labor services." (p. 172). Menger, Carl. 1871 [1976]. Principles of Economics. Trans. James Dingwall and Bert Hoselitz. New York: New York University Press Fred Foldvary