@article{IVM_1968_8_a8,
     author = {I. Yu. Ryzhakov},
     title = {The problem of finding the characteristic set in certain special cases},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {63--72},
     publisher = {mathdoc},
     number = {8},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1968_8_a8/}
}