Wilhelm Röpke (1899-1966) was schooled in the tradition of the Austrians and made enormous contributions to the study of political institutions. His powerful anti-Keynesian writings in particular underscore what an outstanding economist he was and the extent to which he was influenced by Mises. Röpke defended sound money and free trade, and attacked welfare. While some consider him a doubter on free markets, he was in fact a passionate advocate of laissez-faire.
Ludwig von Mises: ". The use of money in a market economy is a praxeologically necessary fact. That gold, and not something else, is used as money is merely a historical fact and as such cannot be conceived by catallactics." - Human Action