Babbie, Earl R., author
Wadsworth and Cengage Learning, 2013 (International edition)
Buku Teks
Judd, Charles M., author
Methuen, 1991
Buku Teks
Babbie, Earl R., author
Cengage Learning, 2016
Buku Teks
Louise H. Kidder
Holt, Rinehart and Winston, 1981
Buku Teks
Lee, Raymond M., author
Open University Press, 2000
Buku Teks SO