@misc{indiciae71263147fcf7,
  title = {Analytical results of insoluble-residue samples from the Paducah 1 degree x 2 degrees Quadrangle, Missouri, Illinois, and Kentucky; drill hole Nos. P1-P20},
  author = {John H. Bullock and H. W. Folger and J. D. Sharkey and J.R. Gillison and C. D. Taylor},
  year = {1991},
  doi = {10.3133/ofr91378a},
  url = {https://pubs.usgs.gov/publication/ofr91378A},
  note = {Source identifier: ofr91378A}
}