TY  - JOUR
AU  - R. F. Polishchuk
TI  - On the classification of the curvature tensor by means of principal congruences
JO  - Doklady Akademii Nauk
PY  - 1970
SP  - 62
EP  - 65
VL  - 194
IS  - 1
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DAN_1970_194_1_a15/
LA  - ru
ID  - DAN_1970_194_1_a15
ER  -