Colombian Petroleum Company, Cucuta, Colombia. Stratigraphy of the Southern Barco Concession. Santander del Norte, Colombia, January 1932, Box: 5, Folder: 12. Hollis Hedberg papers, RH MS 546. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/149122 Accessed April 29, 2024.