@article{MZ_1980__172_172941,
     author = {Harold Donnelly and Peter Li},
     title = {Lower {Bounds} for the {Eigenvalues} of {Negatively} {Curved} {Manifolds.}},
     journal = {Mathematische Zeitschrift},
     pages = {29--40},
     publisher = {mathdoc},
     volume = {172},
     year = {1980},
     zbl = {0413.58020},
     url = {http://geodesic.mathdoc.fr/item/MZ_1980__172_172941/}
}