@article{8424,
  author = {L. Rosenberg},
  title = {Gauge-invariant approximations for scattering in a strong external field},
  year = {1986},
  journal = {Physical Review A},
  volume = {34},
  pages = {978-985},
  month = {Jan-08-1986},
  issn = {0556-2791},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.34.978},
  doi = {10.1103/PhysRevA.34.978},
}