@article{11605,
  author = {D. van Blerkom},
  title = {Radiative excitation in planetary nebulae},
  year = {1969},
  journal = {Monthly Notices of the Royal Astronomical Society},
  volume = {145},
  pages = {75\textendash90},
  url = {http://adsabs.harvard.edu/full/1969MNRAS.145...75V},
  doi = {10.1093/mnras/145.1.75},
  note = {JILA Pub. 519},
}