Russel, Bertrand, author
Routledge, 1948
Buku Teks
edited by Dagobert D. Runes
Littlefield, Adams, 1962
Buku Teks
Mayer, Frederick, author
American Book Company, 1951
Buku Teks
Mayer, Frederick, author
American Book Company, 1951
Buku Klasik
De Wulf, Maurice
Dover Publications, Inc., 1922
Buku Teks