1. Neustadt, L. W.,Optimal Control Problems as Extremal Problems in a Banach Space, Proceedings of the Symposium on System Theory, Polytechnic Institute of Brooklyn, Brooklyn, New York, 1965.
2. Halkin, H.,Finite Convexity in Infinite-Dimensional Spaces, Proceedings of the Colloquium on Convexity, Edited by W. Fenchel, University of Copenhagen, Mathematical Institute, Copenhagen, 1965.
3. Neustadt, L. W.,An Abstract Variational Theory with Applications to a Broad Class of Optimization Problems 1: General Theory, SIAM Journal on Control, Vol. 4, No. 3, 1966.
4. Halkin, H.,An Abstract Framework for the Theory of Process Optimization, Bulletin of the American Mathematical Society, Vol. 72, No. 4, 1966.
5. Halkin, H.,Optimal Control as Programming in Infinite Dimensional Spaces, CIME: Calculus of Variations, Classical and Modern, Edizioni Cremonese, Roma, 1966.