@misc{indiciaef4ed1c892d22,
  title = {The Mississippian and Pennsylvanian (Carboniferous) systems in the United States},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1979},
  doi = {10.3133/pp1110al},
  url = {https://pubs.usgs.gov/publication/pp1110AL},
  note = {Source identifier: pp1110AL}
}