@article{702410,
     title = {Lectures on Lyusternik-Schnirelman theory for indefinite nonlinear eigenvalue problems and its applications},
     booktitle = {Nonlinear Analysis, Function Spaces and Applications},
     series = {GDML\_Books},
     publisher = {BSB B. G. Teubner Verlagsgesellschaft},
     address = {Leipzig},
     year = {1979},
     pages = {176-219},
     mrnumber = {MR0578914},
     zbl = {0411.47040},
     url = {http://dml.mathdoc.fr/item/702410}
}

Zeidler, Eberhard. Lectures on Lyusternik-Schnirelman theory for indefinite nonlinear eigenvalue problems and its applications, dans Nonlinear Analysis, Function Spaces and Applications, GDML_Books,  (1979), pp. 176-219. http://gdmltest.u-ga.fr/item/702410/