1. Barnow, B. S. The effects of Head Start and socioeconomic status on cognitive development of disadvantaged children. Unpublished doctoral dissertation, University of Wisconsin, Department of Economics, 1973.
2. Reforms as experiments;Campbell;American Psychologist,1969
3. How regression artifacts in quasi-experimental evaluations can mistakenly make compensatory education look harmful;Campbell,1970
4. Selection bias in evaluating treatment effects: Some formal illustrations;Goldberger,1972
5. Selection bias in evaluating treatment effects: The case of interaction;Goldberger,1972