@article{CMUC_1965__6_2_a1,
     author = {Vop\v{e}nka, Petr and Pultr, Ale\v{s} and Hedrl{\'\i}n, Zden\v{e}k},
     title = {A rigid relation exists on any set},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {149--155},
     publisher = {mathdoc},
     volume = {06},
     number = {2},
     year = {1965},
     mrnumber = {0183647},
     zbl = {0149.01402},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1965__6_2_a1/}
}