1. Achen, Christopher H. 1986. The statistical analysis of quasi-experiments. Berkeley: University of California Press.
2. Agresti, Alan. 1996. An introduction to categorical data analysis. New York: Wiley.
3. Ansolabehere, Stephen, Shanto Iyengar, and Adam Simon. 1999. Replicating experiments using aggregate and survey data: The case of negative advertising and turnouts. American Political Science Review 93: 901–909.
4. Berk, Richard A. 1988. Causal inference for sociological data. In Handbook of sociology, ed. Neil J. Smelser, 155–172. Newbury Park, CA: Sage.
5. Blalock Jr., Hubert M. [1961] 1964. Causal inferences in nonexperimental research. Chapel Hill: University of North Carolina Press.