TY - JOUR TI - [unknown] JO - Acta mathematica Universitatis Comenianae PY - 1983 SP - 193 EP - 196 VL - 42-43 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/AMUC_1983__42-43_185854/ ID - AMUC_1983__42-43_185854 ER -