@conference{7661,
  author = {David Hummer},
  title = {Radiative transfer problems in planetary nebulae},
  year = {1983},
  month = {00/1983},
  publisher = {Dordrecht, D. Reidel Publishing Co.},
  address = {London, England},
  url = {http://adsabs.harvard.edu/full/1983IAUS..103..211H},
  note = {JILA Pub. 2573},
}