@article{CMUC_1968__9_2_a5,
     author = {Trnkov\'a, V\v{e}ra},
     title = {Strong embedding of category of all groupoids into category of semigroups},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {251--256},
     publisher = {mathdoc},
     volume = {09},
     number = {2},
     year = {1968},
     mrnumber = {0237394},
     zbl = {0191.01302},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1968__9_2_a5/}
}