@Article{ 
  fermar05,
  author = { Ferriero, Alessandro and Marchini, Elsa },
  title = { On the validity of the Euler-Lagrange equation },
  journal = { J. Math. Anal. Appl. },
  year = { 2005 },
  volume = { 304 },
  number = { 1 },
  pages = { 356-369 },
  URL = { http://cvgmt.sns.it/paper/546/ },
  note = { cvgmt preprint}
}