Gregory, P. R. (1999). Comparative economic systems. Houghton Mifflin.
Lua i Stíl Chicago (17ú heag.)Gregory, Paul R. Comparative Economic Systems. Houghton Mifflin, 1999.
Lua MLA (8ú heag.)Gregory, Paul R. Comparative Economic Systems. Houghton Mifflin, 1999.
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