Thurman, Harold V.
Charles E. Merrill Publishing Company, 1975
Buku Teks
Thurman, Harold U.
Merril Publishing company , 1988
Buku Teks
Yasso, Warren E.
New York: Holt, Rinehart and Winston, 1965
Buku Teks
Yasso, Warren E.
New York: Holt, Rinehart and Winston, 1965
Buku Teks
edited by Richard C. Vetter
Voice of America, 1974
Buku Teks