[1] FUČÍK S., KRBEC M.: Boundary value problems with bounded nonlinearity and general nullspace of the linear part. Math. Z. 155 (1977), 129-138. MR 0473513

[2] HESS P.: A remark on the preceding paper of Fučík and Krbec. Math. Z. 155 (1977), 139-141. MR 0473514 | Zbl 0356.35030

[3] FIGUEIREDO D. G., WEI-MING NI: Perturbations of second order linear elliptic problems by nonlinearities without Landesman-Lazer condition. Nonlinear Analysis 3 (5) (1979), 629-634. MR 0541873 | Zbl 0429.35035

[4] DRÁBEK P.: Bounded nonlinear perturbations of second order linear elliptic problems. Comment. Math. Univ. Carolina 22 (1981), 215-221. MR 0620358

[5] DRÁBEK P.: Rešimosť nělinejnych někoercitivnych uravněnij. (Russian), in: Proceedings of the VII. Soviet-Czechoslovakian converence on "Theory of functions and functional analysis in mathematical physics" held in Jerevan, 28. 9. - 3. 10. 1981.

[6] CONCALVES J. V. A.: On bounded nonlinear perturbations of and elliptic equation at resonance. Nonlinear Analysis 1 (5) (1981), 57-60. MR 0597281

[7] SITNIKOVÁ E. G.: Těorema o silnom nule dlja elliptičeskogo uravněnija vysokogo porjadka. Mat. Sbormik 8 (123) (1970), 376-397. MR 0264219