TY - JOUR TI - [unknown] JO - Acta mathematica Universitatis Comenianae PY - 1983 SP - 133 EP - 144 VL - 42-43 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/AMUC_1983__42-43_185849/ ID - AMUC_1983__42-43_185849 ER -