Sprenger, Polly, author
Virgin, 2001
Buku Teks
Kirkpatrick, Donald L., author
American Society for Training & Development, 2006
eBooks
Levenstern, Mary Kerney
Avery Publ. , 1992
Buku Teks
Beach, Mark, author
Writer's Digest Books, 1994
Buku Teks
Talbot, Marianne, author
Yayasan Obor Indonesia, 2005
Buku Teks