[1] Amann H., Ambrosetti A., Mancini G.: 
Elliptic equations with noniveriible Fredholm linear part and bounded nonlinearities. Math. Z. 158 (1978), 179-194. 
MR 0481498[2] Bers L., John F., Schechter M.: 
Partial Differential Equations. Interecience, New York, 1964. 
MR 0163043 | 
Zbl 0126.00207[3] Drábek P.: 
Bounded nonlinear perturbations of second order linear elliptic problems. Comment. Math. Univ. Carolinae 22 (1981), 215-221. 
MR 0620358[4] Drábek P.: 
On the resonance problem with nonlinearity which has arbitrary linear growth. J. Math. Analysis and Appl. 127 (1987), 435-442. 
MR 0915069[5] de Figueiredo D. G., Ming-Ni W.: 
Perturbations of second order linear elliptic problems by nonlinearities without Landesman - Lazer condition. Nonlinear Analysis T.M.A. 3 (1979), 629-634. 
MR 0541873[6] Gupta Ch. P.: 
Solvability of a boundary value problem with the nonlinearity satisfying a sign condition. J. Math. Analysis and Appl. 129 (1988), 482-492. 
MR 0924305 | 
Zbl 0638.34015[7] Iannacci R., Nkashama M. N., Ward J. R., Jr.: 
Nonlinear second order elliptic partial differential equations at resonance. Trans. Amer. Math. Society 311 (1989), 711-726. 
MR 0951886 | 
Zbl 0686.35045[8] Kufner A., John O., Fučík S.: 
Function Spaces. Academia, Praha, 1977. 
MR 0482102