[1] Altman M.: Stationary points in non-linear programming. Bull. Acad. Polon. Sci., math., astr., phys. 12 (1964), No 1, 29-35. MR 0164810 | Zbl 0123.37302

[2] Altman M.: A feasible direction method for solving the non-linear programming problem. Bull. Acad. Polon. Sci., math., astr., phys. 12 (1964), No 1, 43-50. MR 0165665 | Zbl 0127.36705

[3] Zoutendijk G.: Methods of feasible directions. Elsevier, Amsterdam 1960. Zbl 0097.35408

[4] Kirchgässner K., Ritter K.: On stationary points of nonlinear maximum-problems in Banach spaces. J. SIAM Control 4 (1966), No 4, 732-739. MR 0202016