Ritter, C. (1968). The essence of Plato's philosophy. Russell & Russell.
Lua i Stíl Chicago (17ú heag.)Ritter, Constantin. The Essence of Plato's Philosophy. New York: Russell & Russell, 1968.
Lua MLA (9ú heag.)Ritter, Constantin. The Essence of Plato's Philosophy. Russell & Russell, 1968.
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