Davies, Ivor K., author
McGraw-Hill, 1971
Buku Teks
Pountney, Jackie, author
Learning Matters, 2011
Buku Teks
Numrich, Carol
Longman, 1994
Buku Teks
Kaleba, Kermit, author
American Society for Training & Development, 2007
eBooks
Larry Israelite, editor
American Society for Training & Development, 2010
eBooks