@Misc{ 
  Spe18,
  author = { Spector, Daniel },
  title = { An Optimal Sobolev Embedding for $L^1$ },
  journal = {  },
  year = { 2018 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3928/ },
  note = { cvgmt preprint}
}