Snell, E.J.
Chapman and Hall, 1991
Buku Referensi
Ryan, Barbara
Brooks/Cole Cengage Learning, 2013
Buku Teks
Kohler, Ulrich
Stata Press, 2009
Buku Teks
Hjorth, J. S. Urban
Chapman & Hall, 1994
Buku Teks
Kennedy, William J.
Marcel Dekker, 1980
Buku Teks