@misc{indiciae49d85eb2168a,
  title = {Theorem for functional derivatives in density-functional theory.},
  author = {H Ou-Yang and M Levy},
  year = {1991},
  doi = {10.1103/physreva.44.54},
  url = {https://pubmed.ncbi.nlm.nih.gov/9905653/},
  note = {Source identifier: 9905653}
}