References
- Bracht, G. H.; Glass, G. V, “The External Validity of Experiments,” American Educational Research Journal, 5:437–474, 1968.
- Campbell, D. T.; Stanley, J. C., Experimental and Quasi-Experimental Designs for Research, Rand McNally, Chicago, 1963.
- Helmstadter, G. C., Research Concepts in Human Behavior: Education, Psychology, Sociology, Appleton-Century-Crofts, New York, 1970.
- Kerlinger, F. N., Foundations of Behavioral Research, Holt, Rinehart, and Winston, New York, 1964.
- Solomon, R. L., “An Extension of Control Group Design,” Psychological Bulletin, 46:137–150, 1949.