edited by Richard L. Watson
The Free Press, 1968
Buku Teks
Whittaker, David J., author
Routledge, 1997
Buku Teks
Rae, John B.
Mc Graw-Hill Book Company, 1949
Buku Teks
Stebbins, Richard P., author
Harper & Row, 1963
Buku Teks
Buchanan, Albert Russell, author
Harper & Row, 1964
Buku Teks