@misc{indiciaec6317bc1bf33,
  title = {Estimating sunspot number},
  author = {Wilson, R. M. and Reichmann, E. J. and Teuber, D. L.},
  year = {1984},
  url = {https://ntrs.nasa.gov/citations/19850002588},
  note = {Source identifier: 19850002588}
}