@misc{indiciaee0650dda5acf,
  title = {GIS Representation of Coal-Bearing Areas in Africa},
  author = {Matthew D. Merrill and Susan J. Tewalt},
  year = {2008},
  doi = {10.3133/ofr20081258},
  url = {https://pubs.usgs.gov/publication/ofr20081258},
  note = {Source identifier: ofr20081258}
}