@article{etna_vol55_pp1-75,
  author  = {J\"org Lampe and Heinrich Voss},
  title   = {A survey on variational characterizations for nonlinear eigenvalue problems},
  journal = {Electron. Trans. Numer. Anal.},
  volume  = {55},
  year    = {2022},
  pages   = {1--75},
  doi     = {10.1553/etna_vol55s1},
}