@misc{AMUC_1990__56-57_186066,
     title = {[unknown]},
     journal = {Acta mathematica Universitatis Comenianae},
     pages = {11--18},
     year = {1990},
     volume = {56-57},
     url = {http://geodesic.mathdoc.fr/item/AMUC_1990__56-57_186066/}
}