Williams, Lloyd; Hershey, Robert E.; Abernethy, R. F.; Gandrud, B. W. & Reynolds, D. A. Estimate of Known Recoverable Reserves and the Preparation and Carbonizing Properties of Coking Coal in Sequatchie County, Tennessee, report, July 1955; (https://digital.library.unt.edu/ark:/67531/metadc38625/m1/1/: accessed October 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .