Libby, Robert, author
Irwin McGraw-Hill, 2001
Buku Teks
Short, Daniel G., author
Richard D. Irwin, 1990
Buku Teks
Rachlin, Robert, author
American Management Association, 1996
eBooks
Slavin, Albert, author
Holt Rinehart and Winston, 1972
Buku Teks
Knapp, Michael C., author
Ohio South-Western, 1998
Buku Teks