Travers, Kenneth J.
Laidlaw Brothers, 1987
Buku Teks
Jurgensen, Ray C.
Houghton-Miffiln, 1983
Buku Teks
Brumfiel, Charles Francis, 1914-
Addison-Wesley, 1962
Buku Teks
Schapiro, J. Salwyn
D. Van Nostrand, 1958
Buku Teks
Snyder, Louis L.
D. Van Nostrand Company, 1958
Buku Teks