1. The growth of systematic thinking: Replication and analysis of piaget's first chemical experiment
2. Thought and choice in chess. The Hague: Mouton, 1965.
3. Piagetian task in a black box: Chemical experiment I. Unpublished manuscript, Iowa State University. All patent rights to the electronic task are reserved by the Iowa State University Research Foundation, November 28, 1975.
4. Measurement of logical thinking: An electronic equivalent of Piaget's first chemical experiment. Paper presented at the annual convention of the National Association for Research in Science Teaching, Cincinnati, Ohio, March 1977.
5. Sex differences in problem-solving ability