@misc{indiciae7b469460e814,
  title = {Map of mineral resources, Prince Georges County, Maryland},
  author = {J.T. Hack},
  year = {1976},
  doi = {10.3133/mf768a},
  url = {https://pubs.usgs.gov/publication/mf768A},
  note = {Source identifier: mf768A}
}