Maxwell, John C.
NY : Center Street, 2014
Buku Teks
Laurel, Deborah Spring
American Society for Training & Development, 2008
eBooks
Heng, Paul
Prentice-Hall, 2001
Buku Teks
Wee, Heng Neo
Pearson Prentice Hall, 2004
Buku Teks
Greene, Gardiner G.
McGraw-Hill, 1975
Buku Teks