@misc{AMUC_1987__48-49_185962,
     title = {[unknown]},
     journal = {Acta mathematica Universitatis Comenianae},
     pages = {51--62},
     publisher = {mathdoc},
     volume = {48-49},
     year = {1987},
     url = {http://geodesic.mathdoc.fr/item/AMUC_1987__48-49_185962/}
}