DC Heath and Company , 1980
Buku Teks
Cambridge University Press, 2009
eBooks
Blazek, Ron, author
Libraries Unlimited, 2000
Buku Referensi
Michael Nelson, Martha Craven Nussbaum, James V. Mirollo, Mera J. Flaumenhaft
Jossey-Bass, 2000
Buku Teks
Kaufmann, Walter, editor
Reader's Digest Press, 1977
Buku Teks