Timberlake, Richard H.
N.Y. Harper & Row , 1965
Buku Teks
Kent, Raymond P., author
Holt, Rinehart & Winston, 1947
Buku Teks
Savage, Donald T., author
John Wiley & Sons, 1977
Buku Teks
Bradford, Frederick A., author
Longmans, Green, 1939
Buku Teks
Klise, Eugene S., author
South-Western College Publishing, 1972
Buku Teks