1. H. Frankowska, An open mapping principle for set-valued maps, Centre de Récherches Mathématiques, Université de Montréal, rapport CRM-1344 (1986).
2. H. Frankowska, Local controllability of control systems with feedback, Centre de Récherches Mathématiques, Université de Montréal, rapport CRM-1364 (1986).
3. M. Kawski, Control variations and local controllability, Proceedings of MTNS 1987, C. I. Byrnes, C. F. Martin and R. Saeks, eds., Elsevier Science Publishers, North Holland.
4. A. Krener, The high order maximal principle and its applications to singular extremals, SIAM J. Control and Optimization, 15, (1977) pp. 256–293
5. E. B. Lee and L. Markus, Foundations of Optimal Control Theory, Wiley, 1967.