Baker, Richard E., author
McGraw-Hill, 1999
Buku Referensi
edited by W.A. Paton
Ronald Press, 1955
Buku Teks
Coombs, William E., author
McGraw-Hill, 1984
Buku Referensi
Prentice-Hall, 1991
Buku Referensi
Diamond, Michael A., author
South-Western Publishing, 1993
Buku Teks