@article{MAN_1972__199_162321,
     author = {Grigorios Tsagas},
     title = {The {Closed} {Geodesics} of a {Special} {Manifold.}},
     journal = {Mathematische Annalen},
     pages = {155--160},
     publisher = {mathdoc},
     volume = {199},
     year = {1972},
     zbl = {0285.53037},
     url = {http://geodesic.mathdoc.fr/item/MAN_1972__199_162321/}
}