@Article{ 
  betorlsme03,
  author = { Bethuel, Fabrice and Orlandi, Giandomenico and Smets, Didier },
  title = { Vortex rings for the Gross-Pitaevskii equation },
  journal = { J. Eur. Math. Soc. },
  year = { 2004 },
  volume = { 6 },
  number = { 1 },
  pages = { 17-94 },
  URL = { http://cvgmt.sns.it/paper/872/ },
  note = { cvgmt preprint}
}