@Misc{ 
  DelGavPis17a,
  author = { Della Pietra, Francesco and Gavitone, Nunzia and Piscitelli, Gianpaolo },
  title = { On the second Dirichlet eigenvalue of some nonlinear anisotropic
  elliptic operators },
  journal = {  },
  year = { 2017 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/5706/ },
  note = { cvgmt preprint}
}