@misc{indiciae537f7357bf2e,
  title = {Analytical results of insoluble-residue samples from the Paducah 1 degree x 2 degrees Quadrangle, Missouri, Illinois and Kentucky; Drill hole nos. I18-I29 (excluding I23)},
  author = {John H. Bullock and H. W. Folger and J. D. Sharkey and C. D. Taylor},
  year = {1991},
  doi = {10.3133/ofr91621a},
  url = {https://pubs.usgs.gov/publication/ofr91621A},
  note = {Source identifier: ofr91621A}
}