AAPG "Causality and timing in the North American Transgression-Regression Cycle from Cambrian to Present." By Walter S. Olson, July 1977, Box: 55, Folder: 19. Hollis Hedberg papers, RH MS 546. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/150631 Accessed June 25, 2025.