@article{PPN588886025+DMDLOG_0015,
     title = {Chapter XI. Exposition of the principles of the calculus of variations.},
     booktitle = {Integral Calculus, and Calculus of Variations Vol. II},
     series = {GDML\_Books},
     publisher = {UP},
     address = {Oxford},
     year = {1854},
     pages = {234},
     url = {http://dml.mathdoc.fr/item/PPN588886025+DMDLOG_0015}
}