@Misc{ 
  delspa,
  author = { De Lellis, Camillo and Spadaro, Emanuele },
  title = { Center manifold: a case study },
  journal = { Discrete Contin. Dyn. Syst. },
  year = { 2011 },
  volume = { 31 },
  number = { 4 },
  pages = { 1249-1272 },
  URL = { http://cvgmt.sns.it/paper/1117/ },
  note = { cvgmt preprint}
}