@article{IVM_1962_6_a0,
     author = {M. A. Akivis},
     title = {Transformations of surfaces by focal families of rays.},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {3--13},
     year = {1962},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1962_6_a0/}
}