@article{1183419223,
author = {Mason, Max},
title = {A necessary condition for an extremum of a double integral},
journal = {Bull. Amer. Math. Soc.},
volume = {14},
number = {3},
year = {1907},
pages = { 293-298},
language = {en},
url = {http://dml.mathdoc.fr/item/1183419223}
}
Mason, Max. A necessary condition for an extremum of a double integral. Bull. Amer. Math. Soc., Tome 14 (1907) no. 3, pp. 293-298. http://gdmltest.u-ga.fr/item/1183419223/