TY  - JOUR
AU  - S. CARTER
AU  - S.A. ROBERTSON
TI  - Relations Between a Manifold and its Focal Set.
JO  - Inventiones mathematicae
PY  - 1967
SP  - 300
EP  - 307
VL  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/IM_1967__3_141877/
ID  - IM_1967__3_141877
ER  -