@misc{AMUC_1987__50-51_185991,
     title = {[unknown]},
     journal = {Acta mathematica Universitatis Comenianae},
     pages = {15--26},
     year = {1987},
     volume = {50-51},
     url = {http://geodesic.mathdoc.fr/item/AMUC_1987__50-51_185991/}
}