Hall, Patrick A.V., author
Macdonald and Jane`s, 1975
Buku Teks
Fisher, Robert C.
Dickenson Publishing Company, Inc., 1970
Buku Teks
Travers, Kenneth J., author
Laidlaw Brothers, 1987
Buku Teks
Brumfiel, Charles Francis, 1914-, author
Addison-Wesley, 1962
Buku Teks
Jurgensen, Ray C., author
Houghton-Miffiln, 1983
Buku Teks