@article{AIHPC_1988__5_2_119_0,
     author = {Szulkin, Andrzej},
     title = {Ljusternik-Schnirelmann theory on $C^1$-manifolds},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {119--139},
     publisher = {Gauthier-Villars},
     volume = {5},
     number = {2},
     year = {1988},
     mrnumber = {954468},
     zbl = {0661.58009},
     language = {en},
     url = {http://www.numdam.org/item/AIHPC_1988__5_2_119_0/}
}