@Article{ 
  cupdackne09,
  author = { Cupini, Giovanni and Dacorogna, Bernard and Kneuss, Olivier },
  title = { On the equation $\det \,Du=f$ with no sign hypothesis },
  journal = { Calc. Var. Partial Differential Equations },
  year = { 2009 },
  volume = { 36 },
  pages = { 251-283 },
  URL = { http://cvgmt.sns.it/paper/787/ },
  note = { cvgmt preprint}
}