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@article{IVM_1971_7_a9, author = {N. V. Stepanov}, title = {Fundamental properties of $E$-groups on the plane}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {71--80}, publisher = {mathdoc}, number = {7}, year = {1971}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1971_7_a9/} }
N. V. Stepanov. Fundamental properties of $E$-groups on the plane. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 7 (1971), pp. 71-80. http://geodesic.mathdoc.fr/item/IVM_1971_7_a9/