1. Attribute- and rule-learning aspects of conceptual behaviour;Haygood;Psychological Review,1965
2. The growth of logical thinking;Inhelder,1958
3. How implication is understood;Johnson-Laird;American Journal of Psychology,1969
4. Insight into a logical relation;Johnson-Laird;Quarterly Journal of Experimental Psychology,1970
5. Conditional concept attainment as a function of if factor complexity and then factor complexity;Laughlin;Journal of Experimental Psychology,1968