@misc{indiciae20edd17ac80d,
  title = {Overview and USGS activities},
  author = {Robert B. McEwen and Hugh W. Calkins},
  year = {1983},
  doi = {10.3133/cir895a},
  url = {https://pubs.usgs.gov/publication/cir895A},
  note = {Source identifier: cir895A}
}