@Article{ 
  FerFig20,
  author = { Fernández-Real, Xavier and Figalli, Alessio },
  title = { On the obstacle problem for the 1D wave equation },
  journal = { Mathematics in Engineering },
  year = { 2020 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/4583/ },
  note = { cvgmt preprint}
}