edited by Howard S. Elllis
Blakiston, 1949
Buku Teks
Spencer, Milton H.
Worth, 1971
Buku Teks
Hicks, John
Oxford Univeristy Press , 1965
Buku Teks SO
McEachern, William A.
South-Western College Publishing, 1988
Buku Teks
edited by David Greenaway, Michael Bleaney, and Ian Stewart
Routledge, 1991
Buku Referensi