The conditions which the solution of this optimum problem must satisfy have been fully worked out
and can be stated best in mathematical form: put at their briefest, they are that the marginal rates
of substitution between any two commodities or factors must be the same in all their different uses.
The Use of Knowledge in Society, 1945; available at:
< http://www.econlib.org/library/Essays/hykKnw1.html >
