@article{CMUC_1968_9_1_a8,
     author = {Havel, V\'aclav},
     title = {Nets and groupoids. {II}},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {87--93},
     year = {1968},
     volume = {9},
     number = {1},
     mrnumber = {0231275},
     zbl = {0162.24002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1968_9_1_a8/}
}