@Article{ 
  BogVel13,
  author = { Bogosel, Beniamin and Velichkov, Bozhidar },
  title = { A multiphase shape optimization problem for eigenvalues: qualitative study and numerical results },
  journal = { SIAM Numer. Anal. },
  year = { 2013 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/2303/ },
  note = { cvgmt preprint}
}