@article{DAN_1991_320_5_a3,
     author = {F. G. Maksudov and M. A. Sadygov},
     title = {A higher-order subdifferential},
     journal = {Doklady Akademii Nauk},
     pages = {1049--1053},
     year = {1991},
     volume = {320},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_320_5_a3/}
}