@article{7581,
  author = {David Hummer},
  title = {The generalized exponential-integral and computer algorithms for y = 0, 1},
  year = {1983},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  volume = {30},
  pages = {281-287},
  month = {Jan-09-1983},
  issn = {00224073},
  doi = {10.1016/0022-4073(83)90064-X},
}