@article{1183417176, author = {Hedrick, E. R.}, title = {On the sufficient conditions in the calculus of variations}, journal = {Bull. Amer. Math. Soc.}, volume = {9}, number = {3}, year = {1902}, pages = { 11-24}, language = {en}, url = {http://dml.mathdoc.fr/item/1183417176} }
Hedrick, E. R. On the sufficient conditions in the calculus of variations. Bull. Amer. Math. Soc., Tome 9 (1902) no. 3, pp. 11-24. http://gdmltest.u-ga.fr/item/1183417176/