Mindanao Terrain Intelligence, prepared by Geological Survey, US Department of the Interior, under direction of Chief of Engineers, U.S. Army, May 1944, mapcase folder: 2. Karl J. Pelzer papers, 4267. Division of Rare and Manuscript Collections. https://archives.library.cornell.edu/repositories/2/archival_objects/1004146 Accessed August 26, 2026.