Parkinson, Claire L., author
G.K. Hall, 1984
Buku Teks
Pasadena : Salem Press., 1994
Buku Referensi
Robert M. Hutchins, Mortimer J. Adler, editors in chief
Encyclopaedia Britannica, Inc., 1963
Buku Referensi
New York Pocket Books 1957
Buku Teks
Arnold, A., author
Prentice-Hall, 1996
Buku Teks