Presser, Stephen B.
Thomson/West, 2010
Buku Teks
Daniels, Kathy
Chartered Institute of Personnel and Development, 2012
Buku Teks
Madura, Jeff
South-Western College, 2001
Buku Teks
Glos, Raymond E.
South-Western Publishing, 1947
Buku Teks
Hastings, Paul G.
McGraw-Hill, 1974
Buku Teks