@article{GDZPPN002319373, title = {Closed Geodesics on Complete Surfaces.}, journal = {Mathematische Annalen}, volume = {250}, year = {1980}, pages = {83-96}, zbl = {0422.53024}, url = {http://dml.mathdoc.fr/item/GDZPPN002319373} }
Bangert, Victor. Closed Geodesics on Complete Surfaces.. Mathematische Annalen, Tome 250 (1980) pp. 83-96. http://gdmltest.u-ga.fr/item/GDZPPN002319373/