Harris, Seymour E.
McGraw-Hill Book Company, Inc., 1962
Buku Teks
Karol, Nathaniel H.
John Wiley & Sons, 1980
Buku Teks
Jordan, Thomas E., author
The Falmer Press, 1989
Buku Teks
Macmillan Information, 1972
Buku Referensi
Macmillan Information, 1972
Buku Referensi