TY - JOUR TI - [unknown] JO - Acta mathematica Universitatis Comenianae PY - 1990 SP - 85 EP - 114 VL - 56-57 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/AMUC_1990__56-57_186051/ ID - AMUC_1990__56-57_186051 ER -