@Article{ 
  NovOka13a,
  author = { Novaga, Matteo and Okabe, Shinya },
  title = { Regularity of the obstacle problem for the parabolic biharmonic equation },
  journal = { Math. Ann. },
  year = { 2015 },
  volume = { 363 },
  number = { 3-4 },
  pages = { 1147-1186 },
  URL = { http://cvgmt.sns.it/paper/2282/ },
  note = { cvgmt preprint}
}