@article{TRSPY_1990_188_a5,
     author = {G. A. Seregin},
     title = {Differential properties of extremals of variational problems in the mechanics of viscoplastic media},
     journal = {Informatics and Automation},
     pages = {117--124},
     publisher = {mathdoc},
     volume = {188},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TRSPY_1990_188_a5/}
}