@article{CMUC_1971_12_2_a11,
     author = {Wichs, Tom\'a\v{s}},
     title = {On minimal semirigid relations},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {359--365},
     year = {1971},
     volume = {12},
     number = {2},
     mrnumber = {0284355},
     zbl = {0214.51203},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1971_12_2_a11/}
}