Lewis, Richard D., author
Remaja Rosdakarya, 1996
Buku Teks
Raines, Claire, author
American Management Association, 2006
eBooks
Pease, Allan, author
Sheldon Press , 1981
Buku Teks
Thiederman, Sondra
Lexington books, 1991
Buku Teks
Simmons, Annette, author
American Management Association, 2007
eBooks