TY - JOUR TI - [unknown] JO - Acta mathematica Universitatis Comenianae PY - 1984 SP - 159 EP - 168 VL - 44-45 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/AMUC_1984__44-45_185884/ ID - AMUC_1984__44-45_185884 ER -