@misc{indiciae855eab8dd94c,
  title = {Analytical results of insoluble-residue samples from the Paducah 1 degree x 2 degrees quadrangle, Missouri, Illinois, and Kentucky: Drill holes nos. K1-K4},
  author = {John H. Bullock and Helen W. Folger and John D. Sharkey and Cliff D. Taylor},
  year = {1991},
  doi = {10.3133/ofr91372a},
  url = {https://pubs.usgs.gov/publication/ofr91372A},
  note = {Source identifier: ofr91372A}
}