@misc{W2005107454,
  author = {D.G. Erbs and S.A. Klein and John A. Duffie},
  title = {Estimation of the diffuse radiation fraction for hourly, daily and monthly-average global radiation},
  year = {1982},
  howpublished = {Solar Energy},
  doi = {https://doi.org/10.1016/0038-092x(82)90302-4}
}