@Misc{ 
  HasShe21,
  author = { Hassannezhad, Asma and Sher, David },
  title = { Nodal count for Dirichlet-to-Neumann operators with potential },
  journal = {  },
  year = { 2021 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/5209/ },
  note = { cvgmt preprint}
}