@misc{indiciaeff13350be335,
  title = {Total-count gamma radiation map of the Bopolu quadrangle, Liberia},
  author = {John Charles Behrendt and Cletus S. Wotorson},
  year = {1971},
  doi = {10.3133/ofr7129},
  url = {https://pubs.usgs.gov/publication/ofr7129},
  note = {Source identifier: ofr7129}
}