no. 5
A general mountain pass principle for locating and classifying critical points
Annales de l'I.H.P. Analyse non linéaire, Tome 6 (1989) no. 5, pp. 321-330. 
@article{AIHPC_1989__6_5_321_0,
     author = {Ghoussoub, Nassif A. and Preiss, D.},
     title = {A general mountain pass principle for locating and classifying critical points},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {321--330},
     publisher = {Gauthier-Villars},
     volume = {6},
     number = {5},
     year = {1989},
     zbl = {0711.58008},
     mrnumber = {1030853},
     language = {en},
     url = {www.numdam.org/item/AIHPC_1989__6_5_321_0/}
}
Ghoussoub, N.; Preiss, D. A general mountain pass principle for locating and classifying critical points. Annales de l'I.H.P. Analyse non linéaire, Tome 6 (1989) no. 5, pp. 321-330. http://www.numdam.org/item/AIHPC_1989__6_5_321_0/

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