Barber, Alfred W., author
Parker Publishing Company, Inc., 1980
Buku Referensi
Genn, Robert C., author
Parker Publishing Company, 1977
Buku Referensi
Markus, John, 1911-, author
McGraw-Hill, 1971
Buku Referensi
Heiserman, David L., author
Prentice-Hall, 1981
Buku Referensi
Hughes, Fredrick W., author
Prentice-Hall, 1983
Buku Referensi