@article{7154,
  author = {A. Pradhan and J. Shull},
  title = {Density and Temperature Diagnostics of X-Ray Sources - Line Ratios for Helium-Like Ions},
  year = {1981},
  journal = {The Astrophysical Journal},
  volume = {249},
  pages = {821},
  month = {Jan-10-1981},
  issn = {0004-637X},
  url = {http://adsabs.harvard.edu/full/1981ApJ...249..821P},
  doi = {10.1086/159340},
}