@misc{indiciae037595607713,
  title = {Modern aerial gamma-ray spectrometry and regional potassium map of the conterminous United States},
  author = {Joseph S. Duval},
  year = {1990},
  doi = {10.1016/0375-6742(90)90076-m},
  url = {https://pubs.usgs.gov/publication/70015815},
  note = {Source identifier: 70015815}
}