@misc{indiciaeff36856906aa,
  title = {Fermat's principle in general relativity.},
  author = {R Nityananda and J Samuel},
  year = {1992},
  doi = {10.1103/physrevd.45.3862},
  url = {https://pubmed.ncbi.nlm.nih.gov/10014279/},
  note = {Source identifier: 10014279}
}