@Misc{ 
  butrie05,
  author = { Buttazzo, Giuseppe and Rieger, Marc Olivier },
  title = { Variational problems for functionals involving the value distribution },
  journal = {  },
  year = { 2005 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/451/ },
  note = { cvgmt preprint}
}