@article{GDZPPN002100827,
title = {A new curvature invariant and entropy of geodesic flow.},
journal = {Inventiones mathematicae},
volume = {75},
year = {1984},
pages = {455-462},
zbl = {0536.53048},
url = {http://dml.mathdoc.fr/item/GDZPPN002100827}
}
Sarnak, P.; Osserman, R. A new curvature invariant and entropy of geodesic flow.. Inventiones mathematicae, Tome 75 (1984) pp. 455-462. http://gdmltest.u-ga.fr/item/GDZPPN002100827/