Genn, Robert C., author
Parker Publishing Company, 1977
Buku Referensi
Lenk, John D., author
McGraw-Hill, 1999
Buku Referensi
Miller, Rex, 1939-2004
McGraw-Hill, 2009
Buku Teks
Lenk, John D., author
McGraw-Hill, 1995
Buku Referensi
Heiserman, David L., author
Prentice-Hall, 1977
Buku Referensi