@article{1077490488,
author = {Morse, Marston},
title = {The index theorem in the calculus of variations},
journal = {Duke Math. J.},
volume = {4},
number = {1},
year = {1938},
pages = { 231-246},
language = {en},
url = {http://dml.mathdoc.fr/item/1077490488}
}
Morse, Marston. The index theorem in the calculus of variations. Duke Math. J., Tome 4 (1938) no. 1, pp. 231-246. http://gdmltest.u-ga.fr/item/1077490488/