AAPG Burkart, Clemons, and Crane, "Mesozoic and Cenozoic Stratigraphy of Southeastern Guatemala", 1972, Box: 55, Folder: 28. Hollis Hedberg papers, RH MS 546. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/150640 Accessed June 21, 2025.