@misc{indiciaec72fffe06998,
  title = {Stratigraphic framework of Cambrian and Ordovician rocks in the central Appalachian basin from Richland County, Ohio, to Rockingham County, Virginia},
  author = {R. T. Ryder},
  year = {1991},
  doi = {10.3133/i2264},
  url = {https://pubs.usgs.gov/publication/i2264},
  note = {Source identifier: i2264}
}