editors, Tim Halliday, Kraig Adler
Facts on File, 1994
Buku Referensi
Carr, Archie
Time Incorporated, 1970
Buku Teks
edited by Frederick W. Stehr
Kendall/Hunt, 1991
Buku Teks
edited by Frederick W. Stehr
Kendall/Hunt, 1987
Buku Teks
Wigglesworth, V.B.
Worth, 1964
Buku Teks