TY  - JOUR
AU  - S. V. Buyalo
TI  - Euclidean planes in three-dimensional manifolds of nonpositive curvature
JO  - Matematičeskie zametki
PY  - 1988
SP  - 103
EP  - 114
VL  - 43
IS  - 1
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MZM_1988_43_1_a11/
LA  - ru
ID  - MZM_1988_43_1_a11
ER  -