@misc{indiciaee2f3da786e91,
  title = {A variational principle for the scattered wave.},
  author = {D E Freund and R A Farrell},
  year = {1990},
  doi = {10.1121/1.399311},
  url = {https://pubmed.ncbi.nlm.nih.gov/2348017/},
  note = {Source identifier: 2348017}
}