SPENCER, D. E. (1990). Study Guide Economics David E. Spencer; Parkin. Addison-Wesley.
Lua i Stíl Chicago (17ú heag.)SPENCER, David E. Study Guide Economics David E. Spencer; Parkin. Addison-Wesley, 1990.
Lua MLA (8ú heag.)SPENCER, David E. Study Guide Economics David E. Spencer; Parkin. Addison-Wesley, 1990.
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