@misc{indiciaea9ccd4b112d5,
  title = {EIGENFUNCTION EXPANSIONS FOR FORMALLY SELF-ADJOINT PARTIAL DIFFERENTIAL OPERATORS. I.},
  author = {F E Browder},
  year = {1956},
  doi = {10.1073/pnas.42.10.769},
  url = {https://pubmed.ncbi.nlm.nih.gov/16589949/},
  note = {Source identifier: 16589949}
}