@Article{ 
  Mai12,
  author = { Mainini, Edoardo },
  title = { On the signed porous medium flow },
  journal = { Netw. Heterog. Media },
  year = { 2012 },
  volume = { 7 },
  number = { 3 },
  pages = { 525-541 },
  URL = { http://cvgmt.sns.it/paper/1902/ },
  note = { cvgmt preprint}
}