Digby, Pete
Clarendon Press , 1989
Buku Teks
Snell, E. J., author
Chapman and Hall, 1991
Buku Referensi
Ryan, Barbara, author
Brooks/Cole Cengage Learning, 2013
Buku Teks
Kohler, Ulrich, author
Stata Press, 2009
Buku Teks
Kennedy, William J.
Marcel Dekker, 1980
Buku Teks