@article{SM_1993_74_1_a5,
     author = {A. I. Subbotin},
     title = {On a~property of the subdifferential},
     journal = {Sbornik. Mathematics},
     pages = {63--78},
     publisher = {mathdoc},
     volume = {74},
     number = {1},
     year = {1993},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1993_74_1_a5/}
}