JournalsaihpcVol. 3, No. 2Volume 3, No. 2 (1986) Annales de l'Institut Henri Poincaré Cpp. 77–109Minimax principles for lower semicontinuous functions and applications to nonlinear boundary value problemsAndrzej Szulkinpp. 111–183Smooth invariant curves of singularities of vector fields on R3Patrick Bonckaert
pp. 77–109Minimax principles for lower semicontinuous functions and applications to nonlinear boundary value problemsAndrzej Szulkin