UK : The Association of Commonwealth Universities, 1988,
Buku Referensi
Meister, Jeanne C
McGraw-Hill, Inc, 1998
Buku Teks
O`Leary, John
QS Quacquarelli Symonds Limited, 2010
Buku Referensi
Feingold, Mordechai
Oxford University Press, 2017
eBooks
Mordechai Feingold, editor
Oxford University Press, 2016
eBooks