1. Causal models, unobserved variables and experimental data;Alwin;American Journal of Sociology,1974
2. Causal inferences in nonexperimental research;Blalock,1964
3. Prospective: Artifact and control;Campbell,1969
4. Experimental and quasi-experimental designs for research on teaching;Campbell,1963
5. Chen, H.T. (in press). Theory-driven evaluations: A comprehensive perspective. Sage.