Babbie, Earl, author
Wadsworth and Cengage Learning, 2013 (International edition)
Buku Teks
Judd, Charles M., author
Methuen, 1991
Buku Teks
Sjoberg, Gideon
Harper & Row Publishers, 1968
Buku Teks
Babbie, Earl, author
Cengage Learning, 2016
Buku Teks
Lee, Raymond M., author
Open University Press, 2000
Buku Teks