Smart, Terry L., author
Holt, Reinhart and Winston, 1987
Buku Teks
Johnson, Elmer D., author
The Scarecrow Press, 1970
Buku Teks
Palmer, R.R. (Robert Roswell), 1909-2002, author
McGraw-Hill, 1950
Buku Teks
London Chancellor Press 1999,
Buku Referensi
Philips, author
Chancellor Press, 1999
Buku Referensi