Leavell, Robert N., author
West Publishing, [date of publication no identified]
Buku Referensi
Hurley, Judith Benn, author
William Morrow and Company, 1994
Buku Referensi
Smyth, Angela, author
Thorsons, 1994
Buku Referensi
Elliot, Rose, author
Chapmans Publisher Ltd., 1994
Buku Referensi
Friedrich W. Dittmar, author
Sterling Publishing Co.Inc, 1999
Buku Teks