@article{RM_1964_19_4_a13,
     author = {V. Ya. Shvarts and I. Sh. Yaroker},
     title = {Extension elements of semigroups with one-sided unity elements},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     year = {1964},
     volume = {19},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1964_19_4_a13/}
}