TY  - DATA
AU  - Eberlein, Patrick
TI  - Surfaces of nonpositive curvature 
T2  - Memoirs of the American Mathematical Society, 
SN  - 9781470405489 (online)
PY  - 1979///
CY  - Providence
PB  - American Mathematical Society
UR  - http://www.ams.org/memo/0218
ER  -