Colombian Petroleum Company, Cucuta, Colombia, Stratigraphy of the Southern Barco Concession, Santander Del Norte, Colombia, 1932, Box: 5, Folder: 6. Hollis Hedberg papers, RH MS 546. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/149116 Accessed November 21, 2024.