@Article{ 
  LerAgr12,
  author = { Agrachev, Andrei and Lerario, Antonio },
  title = { Systems of Quadratic Inequalities },
  journal = { Proc. London Math. Society },
  year = { 2012 },
  doi = { doi: 10.1112/plms/pds010 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/2868/ },
  note = { cvgmt preprint}
}