SPA (Sumatra Planters Association) Circular No. 26/Sepa of April 21, '59 transmitting notice No. Peng - 001/4/59 Medan commander ordering everybody to listen to Soekarno speech on April 22, 1959, 1959-04-21, Box: 21, Folder: 63. Karl J. Pelzer papers, 4267. Division of Rare and Manuscript Collections. https://archives.library.cornell.edu/repositories/2/archival_objects/1003129 Accessed September 02, 2026.