@Misc{ 
  Han17b,
  author = { Han, Bangxian },
  title = { Self-improvement of gradient estimate of heat flows on metric measure  spaces },
  journal = {  },
  year = { 2017 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3643/ },
  note = { cvgmt preprint}
}