@article{JRAM_1971__246_151079,
     author = {Walter Leighton},
     title = {Bounds for conjugate points.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {126--135},
     year = {1971},
     volume = {246},
     zbl = {0208.11001},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1971__246_151079/}
}