Mason, R. S. (1989). Robert Giffen and the Giffen paradox. Philip Allan.
Lua i Stíl Chicago (17ú heag.)Mason, Roger S. Robert Giffen and the Giffen Paradox. Oxford: Philip Allan, 1989.
Lua MLA (9ú heag.)Mason, Roger S. Robert Giffen and the Giffen Paradox. Philip Allan, 1989.
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