Sayre, Wallace S.
Barnes & Noble, 1964
Buku Teks
Posey, Rollin Bennett
Littlefield, Adam, 1958
Buku Teks
Bailey, Stephen K.
Henry Holt, 1957
Buku Teks
OConnor, Karen
Addison Wesley Longman, 2001
Buku Teks
Ferguson, John H.
McGraw-Hill, 1947
Buku Teks