@article{IVM_1966_1_a8,
     author = {F. I. Kagan},
     title = {The operation of an infinitesimal $S$-extension},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {66--78},
     publisher = {mathdoc},
     number = {1},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1966_1_a8/}
}