Christensen, Howard B.
Hoghton Mifflin, 1977
Buku Teks
Sartika Kurniali
PT Gramedia, 2009
Buku Teks
Richman, Larry
[American Management Association, ], 2002
eBooks
Abdul Rahman Saleh
Sagung Seto, 2010
Buku Teks
Litecky, Charles R.
McGraw-Hill, 1987
Buku Teks