@Article{ 
  MazTerVel16,
  author = { Mazzoleni, Dario and Terracini, Susanna and Velichkov, Bozhidar },
  title = { Regularity of the optimal sets for some spectral functionals },
  journal = { Geom. Funct. Anal. },
  year = { 2017 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3157/ },
  note = { cvgmt preprint}
}