Moody, Paul E.
McGraw-Hill, 1983
Buku Teks
Hammond, John S., 1937-, author
Harvard Business School, 1999
Buku Teks
Ibnu Syamsi, author
Bina Aksara, 1989
Buku Teks
Radford, K.J., author
Prushin-Hall, 1974
Buku Teks
edited by Anthony G. McGrew
Manchester University Press, 1985
Buku Teks