@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/