@article{AIHPC_1986__3_6_431_0,
     author = {Mawhin, J. and Willem, M.},
     title = {Critical points of convex perturbations of some indefinite quadratic forms and semi-linear boundary value problems at resonance},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {431--453},
     publisher = {Gauthier-Villars},
     volume = {3},
     number = {6},
     year = {1986},
     mrnumber = {870864},
     zbl = {0678.35091},
     language = {en},
     url = {http://www.numdam.org/item/AIHPC_1986__3_6_431_0/}
}