1. The theory of hierarchies. Logic, Methodology and Philosophy of Science, Proceedings of the 1960 International Congress, Stanford University Press, 1962, pp. 26–37.
2. A note on function quantification
3. Some remarks on infinitely long formulas. Infinitistic Methods, Proceedings of the Symposium on Foundations of Mathematics, Warsaw, 2–9 September 1959, Państwowe Wydawnictwo Naukowe and Pergamon Press, 1961, pp. 167–183.
4. Reductions of higher-order logic. The Theory of Models, Proceedings of the 1963 International Symposium at Berkeley, North-Holland Publishing Co., 1965, pp. 251–264.