Klatte, D., Kummer, B. & Walzebok, R. (1989). Conditions for Optimality and Strong Stability in Nonlinear Programs without assuming Twice Differentiability of Data. IIASA Working Paper. IIASA, Laxenburg, Austria: WP-89-089
Klatte, D. (1983). On the Lipschitz Behavior of Optimal Solutions in Parametric Problems of Quadratic Optimization and Linear Complementarity. IIASA Working Paper. IIASA, Laxenburg, Austria: WP-83-121