@article{TIMB_2012_20_1_a4,
     author = {P. P. Zabreiko},
     title = {Tangential vectors for sets defined with systems of equations},
     journal = {Trudy Instituta matematiki},
     pages = {42--49},
     year = {2012},
     volume = {20},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TIMB_2012_20_1_a4/}
}