TY  - JOUR
TI  - [unknown]
JO  - Acta mathematica Universitatis Comenianae
PY  - 1980
SP  - 9
EP  - 18
VL  - 39
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/AMUC_1980__39_185815/
ID  - AMUC_1980__39_185815
ER  -