@article{01482989,
title = {On necessary conditions in the calculus of variations.},
journal = {Publications de l'Institut Math\'ematique. Nouvelle S\'erie},
volume = {61(75)},
year = {1997},
pages = {61-72},
zbl = {0946.49014},
language = {en},
url = {http://dml.mathdoc.fr/item/01482989}
}
Janković, Vladimir. On necessary conditions in the calculus of variations.. Publications de l'Institut Mathématique. Nouvelle Série, Tome 61(75) (1997) pp. 61-72. http://gdmltest.u-ga.fr/item/01482989/