Ikegwuoha, M. C. (1991). Voegelin's philosophical concept of order and history: From a political perspective. Pontificia Universitas Urbaniana.
Lua i Stíl Chicago (17ú heag.)Ikegwuoha, Michael Chukwunyelunwa. Voegelin's Philosophical Concept of Order and History: From a Political Perspective. Romae: Pontificia Universitas Urbaniana, 1991.
Lua MLA (8ú heag.)Ikegwuoha, Michael Chukwunyelunwa. Voegelin's Philosophical Concept of Order and History: From a Political Perspective. Pontificia Universitas Urbaniana, 1991.
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