@article{DAN_1985_284_3_a1,
     author = {S. S. Kutateladze},
     title = {Nonstandard analysis of tangent cones},
     journal = {Doklady Akademii Nauk},
     pages = {525--527},
     year = {1985},
     volume = {284},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1985_284_3_a1/}
}