Babbie, E. (1989). The practice of social research (5th.ed.). Wadsworth.
Cita Chicago (17th ed.)Babbie, Earl. The Practice of Social Research. 5th.ed. Belmont: Wadsworth, 1989.
Cita MLA (9th ed.)Babbie, Earl. The Practice of Social Research. 5th.ed. Wadsworth, 1989.
Atenció: Aquestes cites poden no estar 100% correctes.