Blackwelder, Richard E.
The Iowa University Press, 1972
Buku Referensi
Bynagle, Hans E.
Libraries Unlimited, 1986
Buku Referensi
Lauterbach, Richard E.
Harper & Brother Publishers, 1945
Buku Teks
Torrey, Theodore W., author
John Wiley & Sons, 1979
Buku Teks
Bateson, FW
Longmans , 1965
Buku Teks