Werbach, Melvyn R.
Thorsons, 1993
Buku Referensi
Murray, Michael T.
Three Rivers Press, 1996
Buku Teks
Stevenson, Gladys T.
John Wiley & Sons, 1960
Buku Teks
Hutchinson, 1959
Buku Referensi
editors, Donald D. Carr, Norman Herz
Pergamon Press, 1989
Buku Referensi