@Misc{ 
  DePFig12a,
  author = { De Philippis, Guido and Figalli, Alessio },
  title = { Optimal regularity of the convex envelope },
  journal = { Trans. Amer. Math. Soc. },
  year = { 2013 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/1818/ },
  note = { cvgmt preprint}
}