@article{CMUC_1978__19_3_a10,
     author = {Efimov, B. A. and Chertanov, G. I.},
     title = {{\CYRO} {\cyrp}{\cyro}{\cyrd}{\cyrp}{\cyrr}{\cyro}{\cyrs}{\cyrt}{\cyrr}{\cyra}{\cyrn}{\cyrs}{\cyrt}{\cyrv}{\cyra}{\cyrh}  $\Sigma$-{\cyrp}{\cyrr}{\cyri}{\cyri}{\cyrz}{\cyrv}{\cyre}{\cyrd}{\cyre}{\cyrn}{\cyri}{\cyrya} {\cyro}{\cyrt}{\cyrr}{\cyre}{\cyrz}{\cyrk}{\cyro}{\cyrv}},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {569--593},
     publisher = {mathdoc},
     volume = {19},
     number = {3},
     year = {1978},
     mrnumber = {0515021},
     zbl = {0413.54005},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1978__19_3_a10/}
}