no. 4
Multiple critical points for variational problems on partially ordered Hilbert spaces
Annales de l'I.H.P. Analyse non linéaire, Tome 7 (1990) no. 4, pp. 287-304. 
@article{AIHPC_1990__7_4_287_0,
     author = {Wysocki, K.},
     title = {Multiple critical points for variational problems on partially ordered {Hilbert} spaces},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {287--304},
     publisher = {Gauthier-Villars},
     volume = {7},
     number = {4},
     year = {1990},
     mrnumber = {1067777},
     zbl = {0709.58013},
     language = {en},
     url = {http://archive.numdam.org/item/AIHPC_1990__7_4_287_0/}
}
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Wysocki, K. Multiple critical points for variational problems on partially ordered Hilbert spaces. Annales de l'I.H.P. Analyse non linéaire, Tome 7 (1990) no. 4, pp. 287-304. http://archive.numdam.org/item/AIHPC_1990__7_4_287_0/

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