Clyde F. Coombs
McGraw-Hill, 2001
Buku Teks
Ginsberg, Gerald L., author
McGraw-Hill, 1990
Buku Teks
Scoles, Graham J., author
Ellis Horwood, 1980
Buku Referensi
Mandl, Matthew, author
Reston Publishing Company, 1980
Buku Referensi
editor, Arthur B. Williams
McGraw-Hill, 1984
Buku Referensi