TY  - JOUR
TI  - [unknown]
JO  - Acta mathematica Universitatis Comenianae
PY  - 1980
SP  - 43
EP  - 52
VL  - 39
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/AMUC_1980__39_185806/
ID  - AMUC_1980__39_185806
ER  -