Russell, Frederick A.
McGraw-Hill Publishing Company, 1988
Buku Teks
Whiting, Percy H.
Dale Carnegie & Associates, Inc., 1979
Buku Teks
Pederson, Carlton A.
Richard D. Irwin, Inc., 1966
Buku Teks
Manning, Gerald L., author
Prentice Hall International, 1998
Buku Teks
Kahn, George N.
Gramedia Pustaka Utama, 1996
Buku Teks