Bailey, Stephen K., author
Voice of America Forum Lectures, 1956
Buku Teks
Moore, John A.
Macmillan Publishing Company, 1985
Buku Teks
Griffith, Ernest S.
London Methuen & Co. 1967,
Buku Teks
"S.Chand ,
Buku Teks
edited by Robert E. DiClerico, Allan S. Hammock
McGraw-Hill, 1992
Buku Teks