Keller, Gary
McGraw-Hill, 2010
Buku Teks
McCrea, Bridget
[American Management Association, ], 2005
eBooks
Randel, Jim
Facts on File Publications, 1986
Buku Teks
Kau, James B.
McGraw-Hill, 1985
Buku Teks
Shilling, James D.
South-Western, 2002
Buku Teks