@Misc{ 
  HeSquZou15,
  author = { He, Xiaoming and Squassina, Marco and Zou, Wenming },
  title = { The Nehari manifold for fractional systems involving critical nonlinearities },
  journal = {  },
  year = { 2015 },
  pages = { 23 },
  URL = { http://cvgmt.sns.it/paper/2787/ },
  note = { cvgmt preprint}
}