@misc{indiciae6f40e1b1fc5e,
  title = {Tonsteins and clay-rich layers in coal-bearing intervals of the Eocene Manning formation, east-central Texas},
  author = {Leslie F. Ruppert and Peter D. Warwick and Sharon S. Crowley and James Pontolillo},
  year = {1994},
  url = {https://pubs.usgs.gov/publication/70195399},
  note = {Source identifier: 70195399}
}