@article{10_21136_CMJ_1970_100982,
     author = {D'Alarcao, Hugo},
     title = {Biregular semigroups. {I}},
     journal = {Czechoslovak Mathematical Journal},
     pages = {544--548},
     publisher = {mathdoc},
     volume = {20},
     number = {4},
     year = {1970},
     doi = {10.21136/CMJ.1970.100982},
     mrnumber = {0268300},
     zbl = {0223.20071},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1970.100982/}
}