On children's quantitative concept of rational number: construct and estimate the sum
In: Proceedings of the fifth annual meeting: Montréal Sept. 29 - Oct. 1, 1983 = actes de la cinquième rencontre annuelle / PME-NA, North American Chapter of the International Group for the Psychology of Mathematics Education, Jg. vol. 2, S. 272-2791983
Inconsistent student behavior in applicational situations of mathematics
In: Proceedings of the Ninth International Conference for the Psychology of Mathematics Education, Jg. vol. 1: Individual contributions, S. 362-3681985