Graddy, Duane B.
Reston , 1985
Buku Teks
Crum, William Leonard
University of California Press, 1953
Buku Teks
Exton, William Jr.
American Management Association , 1972
Buku Teks
Willcocx, William B.
D.C. Health and Company, 1988
Buku Teks
Spragens, William C
University Press of America, 1979
Buku Teks