@article{IVM_1989_10_a5,
     author = {E. S. Lyapin},
     title = {Partial groupoids that can be obtained from semigroups by restrictions and homomorphisms},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {30--36},
     publisher = {mathdoc},
     number = {10},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1989_10_a5/}
}