Ludwig von Mises (1881-1973) was a leading economist of the Austrian School of Economics. His contribution to economics ranges from the critique of socialism and central planning as early as 1921, on the basis or the argument of the impossibility of "socialist" economic calculation, to the analysis of the working of markets and entrepreneurship, bureaucracy theory and monetary theory.
Human action, his masterpiece, available from the LibertyFund library of Economics & Liberty.
Socialism, an economic, sociological and political study of socialism, available from the LibertyFund library of Economics & Liberty.