@article{SM_1968_4_1_a5,
     author = {S. I. Pokhozhaev},
     title = {The set of critical values of a functional},
     journal = {Sbornik. Mathematics},
     pages = {93--98},
     publisher = {mathdoc},
     volume = {4},
     number = {1},
     year = {1968},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1968_4_1_a5/}
}