@misc{indiciae86850b211095,
  title = {Harmonic generation in free-electron lasers.},
  author = {HP Freund and CL Chang and H Bluem},
  year = {1987},
  doi = {10.1103/physreva.36.3218},
  url = {https://pubmed.ncbi.nlm.nih.gov/9899239/},
  note = {Source identifier: 9899239}
}