@article{10_21136_CMJ_1966_100723,
     author = {Petrich, Mario},
     title = {Semigroups certain of whose subsemigroups have identities},
     journal = {Czechoslovak Mathematical Journal},
     pages = {186--198},
     publisher = {mathdoc},
     volume = {16},
     number = {2},
     year = {1966},
     doi = {10.21136/CMJ.1966.100723},
     mrnumber = {0200370},
     zbl = {0143.03203},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1966.100723/}
}