@article{AUPO_1961_2_1_a1,
     author = {Sedl\'a\v{c}ek, Ladislav},
     title = {Grupoidy a grupy s oper\'atory},
     journal = {Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica},
     pages = {33--66},
     year = {1961},
     volume = {2},
     number = {1},
     mrnumber = {0299711},
     zbl = {0234.20029},
     language = {cs},
     url = {http://geodesic.mathdoc.fr/item/AUPO_1961_2_1_a1/}
}