Böhm-Bawerk's Criticism of Marx
Disputation by the Marxist author Rudolf Hilferding.
Marxian Economics
A survey from the History of Economic Thought website with bibliography and links.
Marxism
An article in the Concise Encyclopedia of Economics by David L. Prychitko.
Political Economy
Marx's writings on economics, reactions to Marx's economics and the Glossary of Political Economy from the Encyclopedia of Marxism.
Primer on Marxian Economics
A chapter from the Essential Principles of Economics provided by Drexel University.