@misc{indiciaeabf6aa15f67c,
  title = {The solar activity cycle},
  author = {Rabin, Douglas M. and Devore, C. R. and Sheeley, Neil R., Jr. and Harvey, Karen L. and Hoeksema, J. T.},
  year = {1991},
  url = {https://ntrs.nasa.gov/citations/19920053601},
  note = {Source identifier: 19920053601}
}