@misc{indiciae1520bf4d0707,
  title = {Keldysh approximation, A2, and strong-field ionization.},
  author = {PW Milonni and JR Ackerhalt},
  year = {1989},
  doi = {10.1103/physreva.39.1139},
  url = {https://pubmed.ncbi.nlm.nih.gov/9901350/},
  note = {Source identifier: 9901350}
}