@article{MZ_1990__203_3_174129,
     author = {Harold Donnelly},
     title = {Negative {Curvature} and {Embedded} {Eigenvalues.}},
     journal = {Mathematische Zeitschrift},
     pages = {301--308},
     year = {1990},
     volume = {203},
     number = {3},
     zbl = {0699.53052},
     url = {http://geodesic.mathdoc.fr/item/MZ_1990__203_3_174129/}
}