TY  - JOUR
AU  - Th. Friedrich
TI  - On an equality for 3-dimensional manifolds
JO  - Commentationes Mathematicae
PY  - 1975
SP  -  187
EP  - 188
VL  - 18
IS  - 2
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/articles/10.14708/cm.v18i2.5820/
DO  - 10.14708/cm.v18i2.5820
LA  - pl
ID  - 10_14708_cm_v18i2_5820
ER  -