@misc{AMUC_1981__38_185802,
     title = {[unknown]},
     journal = {Acta mathematica Universitatis Comenianae},
     pages = {53--62},
     year = {1981},
     volume = {38},
     url = {http://geodesic.mathdoc.fr/item/AMUC_1981__38_185802/}
}