@misc{indiciaea0c723a98624,
  title = {Natural gamma aeroradioactivity map of the Pittsburgh area, Pennsylvania, Ohio, West Virginia, and Maryland},
  author = {R. G. Bates},
  year = {1966},
  doi = {10.3133/gp555},
  url = {https://pubs.usgs.gov/publication/gp555},
  note = {Source identifier: gp555}
}