Maritain, Jacques
Philosophical Library, 1951
Buku Teks SO
Kosso, Peter
Cambridge University Press, 1992
Buku Teks SO
Kelsen, Hans
Kegan Paul : Trench : Trubner , 1946
Buku Teks SO
Patrick, George Thomas White
George Allen and Unwin, 1925
Buku Teks SO
Brightman, Edgar Sheffield
Holt, Rinehart and Winston, 1961
Buku Teks SO