@misc{indiciae54c4db8677c7,
  title = {Origin of Pennsylvanian underclay and related seat rocks},
  author = {J. W. Huddle and S. H. Patterson},
  year = {1961},
  doi = {10.1130/0016-7606(1961)72[1643:oopuar]2.0.co;2},
  url = {https://pubs.usgs.gov/publication/70206836},
  note = {Source identifier: 70206836}
}