1. The Practice of Social Research;Babbie,1989
2. High school yearbooks: A nonreactive measure of social isolation in graduates who later become schizophrenic;Barthel;Journal of Abnormal Psychology,1968
3. Designing unobtrusive field experiments in social psychology;Bochner,1979
4. Reforms as experiments;Campbell;American Psychologist,1969
5. Experimental and quasi-experimental designs for research on teaching;Campbell,1963