@Article{ 
  barman08,
  author = { Bardi, Martino and Mannucci, Paola },
  title = { Comparison principles for subelliptic equations of Monge-Ampère type },
  journal = { Boll. Unione Mat. Ital. },
  year = { 2008 },
  volume = { 1, Serie IX },
  number = { 2 },
  pages = { 489-495 },
  URL = { http://cvgmt.sns.it/paper/1088/ },
  note = { cvgmt preprint}
}