@Article{ 
  bucbutvel11,
  author = { Bucur, Dorin and Buttazzo, Giuseppe and Velichkov, Bozhidar },
  title = { Shape Optimization Problems with Internal Constraint },
  journal = { Ann. I. H. Poincare' Anal. Non Lineaire  },
  year = { 2013 },
  volume = { 30 },
  number = { 3 },
  pages = { 467--495 },
  URL = { http://cvgmt.sns.it/paper/352/ },
  note = { cvgmt preprint}
}