Timberlake, Richard H.
N.Y. Harper & Row , 1965
Buku Teks
Bradford, Frederick A., author
Longmans, Green, 1933
Buku Teks
Kent, Raymond P., author
Holt, Rinehart & Winston, [Date of publication not identified]
Buku Teks
Klise, Eugene S., author
South-Western College Publishing, 1972
Buku Teks
Steiner, William Howard, author
Henry Holt, 1956
Buku Teks