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@article{IVM_1969_5_a10, author = {B. M. Shain}, title = {Restrictive bisemigroups of quasi-single-valued binary {relations.~I}}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {73--84}, publisher = {mathdoc}, number = {5}, year = {1969}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1969_5_a10/} }
B. M. Shain. Restrictive bisemigroups of quasi-single-valued binary relations.~I. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 5 (1969), pp. 73-84. http://geodesic.mathdoc.fr/item/IVM_1969_5_a10/