@article{IVM_1992_7_a7,
     author = {Yu. A. Polonskii},
     title = {Ekeland's variational principle and {Lagrange{\textendash}Clarke} extremum conditions in a~lattice-metric space},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {54--59},
     year = {1992},
     number = {7},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1992_7_a7/}
}