Goodwin, Paul
West Sussex : Wiley, 2010
Buku Teks
Thomas N. Ingram...[et al.]
Harcourt College Publishers, 2001
Buku Teks
Bunn, Derek W.
McGraw-Hill, 1984
Buku Teks
edited by Anthony G. McGrew
Manchester University Press, 1985
Buku Teks SO
Behn, Robert D.
Basic Books, 1982
Buku Teks