Ruggiero, G. d. (1921). Modern philosophy. George Allen & Unwin.
Lua i Stíl Chicago (17ú heag.)Ruggiero, Guido de. Modern Philosophy. London: George Allen & Unwin, 1921.
Lua MLA (9ú heag.)Ruggiero, Guido de. Modern Philosophy. George Allen & Unwin, 1921.
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