Geological Department, Venezuela Gulf Oil Company Report on Stratigraphy and Structure of the Rio Socuy-Rio Guasare Area, Dist. of Mara, State of Zulia by H.D. Hedberg, September 1929, Box: 5, Folder: 2. Hollis Hedberg papers, RH MS 546. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/149112 Accessed April 25, 2024.