George Allen and Unwin, 1985
Buku Teks
Dillman, Don A., author
John Wiley & Sons, 2000
Buku Teks
Long, Lori, author
[American Society for Training and Development Press, American Society for Training and Development Press], 2000
eBooks
Schrauf, Robert W, author
Cambridge University Press, 2016
Buku Teks
by H.G. Johnson... [and others]
Macmillan, 1968
Buku Teks