@article{MZ_1977__155_172561,
     author = {Pierre H. B\'erard},
     title = {On the {Wave} {Equation} on a {Compact} {Riemannian} {Manifold} withour {Conjugate} {Points.}},
     journal = {Mathematische Zeitschrift},
     pages = {249--276},
     publisher = {mathdoc},
     volume = {155},
     year = {1977},
     zbl = {0341.35052},
     url = {http://geodesic.mathdoc.fr/item/MZ_1977__155_172561/}
}