TY  - JOUR
AU  - Švec, Alois
TI  - On the existence of parallel normal vector fields of surfaces in $E^4$
JO  - Czechoslovak Mathematical Journal
PY  - 1976
SP  - 297
EP  - 303
VL  - 26
IS  - 2
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1976.101402/
DO  - 10.21136/CMJ.1976.101402
LA  - en
ID  - 10_21136_CMJ_1976_101402
ER  -