@article{CMUC_1964__5_1_a3,
     author = {Hu\v{s}ek, Miroslav},
     title = {$S$-categories},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {37--46},
     publisher = {mathdoc},
     volume = {05},
     number = {1},
     year = {1964},
     mrnumber = {0174027},
     zbl = {0136.19101},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1964__5_1_a3/}
}