Ludwig von Mises earned a doctorate in law and economics from the University of Vienna in 1906. Like Hayek, he argued the inherent instability of Socialism. According to both of these economists, the calculations required to organize a complex society are too variagated to be efficiently estimated by a few men in government positions.
Mises also believed that economic truths cannot be empirically tested. His major work dealing with this belief is,"Human Action". Hayek and Mises could arguably be called the father's of Austrian economics. (As a little side note, he had a dramatic effect on Ayn Rand.)
Works by Ludwig von Mises: