@article{DAN_1961_138_2_a6,
     author = {G. I. Kats},
     title = {Generalization of the group principle of duality},
     journal = {Doklady Akademii Nauk},
     pages = {275--278},
     publisher = {mathdoc},
     volume = {138},
     number = {2},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1961_138_2_a6/}
}