Spalding, K. J.
Basil Blackwell, 1931
Buku Teks
Scanlan, Burt
John Wiley & Sons, 1983
Buku Teks
Qualman, Erik, author
McGraw-Hill, 2012
Buku Teks
Swartz, Greg, author
American Society for Training & Development, 2008
eBooks
Blanchard, Ken, author
William Morrow, 2013
Buku Teks