@article{1077310410, author = {Westreich, David}, title = {Periodic solutions of second order Lagrangian systems}, journal = {Duke Math. J.}, volume = {41}, number = {1}, year = {1974}, pages = { 405-411}, language = {en}, url = {http://dml.mathdoc.fr/item/1077310410} }
Westreich, David. Periodic solutions of second order Lagrangian systems. Duke Math. J., Tome 41 (1974) no. 1, pp. 405-411. http://gdmltest.u-ga.fr/item/1077310410/