Savage, Donald T.
John Wiley & Sons, 1977
Buku Teks
Bradford, Frederick A.
Longmans, Green, 1939
Buku Teks
Klise, Eugene S.
South-Western College Publishing, 1972
Buku Teks
Steiner, William Howard
Henry Holt, 1956
Buku Teks
Bradford, Frederick A.
Longmans, Green, 1933
Buku Teks