Proposed Type Sections for Upper Silurian and Lower Devonian Subsurface Units in Permian Basin, West Texas, by John M. Mills and Margaret A. Hoening, Box: 6, Folder: 8. Wallace E. Pratt papers, RH MS 870. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/34128 Accessed May 19, 2024.