Longman, 1998
Buku Teks
Purinton, Carl E.
The Ronald Press, 1961
Buku Teks
Fucilla, Joseph G.
Follett Publishing Company, 1964
Buku Referensi
Collier, Leonard Dawson
St. Paul's House Warwick Lane, 1973
Buku Teks
Payne, Stanley G.
W.W. Norton, 1970
Buku Teks