Marxism  
   An article in the Concise Encyclopedia of Economics by David L. Prychitko.
   http://www.econlib.org/library/Enc/Marxism.html

Political Economy  
   Marx's writings on economics, reactions to Marx's economics and the Glossary of Political Economy from the Encyclopedia of Marxism.
   http://www.marxists.org/subject/economy/index.htm

Primer on Marxian Economics  
   A chapter from the Essential Principles of Economics provided by Drexel University.
   http://william-king.www.drexel.edu/top/prin/txt/marx/ApxToC.html

Marxian Economics  
   A survey from the History of Economic Thought website with bibliography and links.
   http://cepa.newschool.edu/het/schools/marxian.htm

Böhm-Bawerk's Criticism of Marx  
   Disputation by the Marxist author Rudolf Hilferding.
   http://www.marxists.org/subject/economy/authors/hilfer/index.htm