@Misc{ 
  CorPis21,
  author = { Corbo Esposito, Antonio and Piscitelli, Gianpaolo },
  title = { The Pseudo-orthogonality for Graph $1$-Laplacian Eigenvectors and
  Applications to Higher Cheeger Constants and Data Clustering },
  journal = {  },
  year = { 2021 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/5726/ },
  note = { cvgmt preprint}
}