Oxley, Harold
Gunung Mulia, 1993
Buku Teks
Chevalier, Roger, author
American Management Association, 2007
eBooks
Thomson, George F., author
Institute of Personeel Management, 1975
Buku Teks
Publications International, 2000
Buku Referensi
R.G.H. Siu
McGraw-Hill, 1980
Buku Teks