@misc{indiciae4a28072ea668,
  title = {Organic geochemistry of black shales, marlstones, and oils of Middle Pennsylvanian rocks from the northern Denver and southeastern Powder River basins, Wyoming, Nebraska, and Colorado},
  author = {J.L. Clayton and Augusta Warden and T.A. Daws and P. G. Lillis and G.E. Michael and M. Dawson},
  year = {1992},
  doi = {10.3133/b1917k},
  url = {https://pubs.usgs.gov/publication/b1917K},
  note = {Source identifier: b1917K}
}