Antczak, T.: An $\eta $-approximation approach to nonlinear mathematical programming involving invex functions
. Numer. Funct. Anal. Optim. 25 (2004), 5–6, 423–438. DOI 10.1081/NFA-200042183
| MR 2106268
 Antczak, T.: Saddle points criteria in an $\eta $-approximation approach for nonlinear mathematical programming involving invex functions
. J. Optim. Theory Appl. 132 (2007), 1, 71–87. DOI 10.1007/s10957-006-9069-9
| MR 2303801
 Bazaraa, M. S., Sherali, H. D., Shetty, C. M.: Nonlinear Programming: Theory and Algorithms
. John Wiley and Sons, New York 1991. MR 2218478
 Bector, C. R., Bector, B. K.: (Generalized)-bonvex functions and second order duality for a nonlinear programming problem. Congr. Numer. 52 (1985), 37–52.
 Bector, C. R., Bector, B. K.: On various duality theorems for second order duality in nonlinear programming
. Cahiers Centre Études Rech. Opér. 28 (1986), 283–292. MR 0885768
| Zbl 0622.90068
 Bector, C. R., Chandra, S.: Generalized Bonvex Functions and Second Order Duality in Mathematical Programming. Research Report No. 85-2, Department of Actuarial and Management Sciences, University of Manitoba, Winnepeg, Manitoba 1985.