@Misc{ 
  FelLivOgn23,
  author = { Felli, Veronica and Liverani, Lorenzo and Ognibene, Roberto },
  title = { Quantitative spectral stability for the Neumann Laplacian in domains
  with small holes },
  journal = {  },
  year = { 2023 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/6302/ },
  note = { cvgmt preprint}
}