@Misc{ 
  Woj16,
  author = { Wojtowytsch, Stephan },
  title = { Helfrich's Energy and Constrained Minimisation },
  journal = {  },
  year = { 2016 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3221/ },
  note = { cvgmt preprint}
}