Otto Pieper. Interview, 1977., 1647-1B4-S650, Box: 1-S628-S630-S649-S650-S651. Southwest Minnesota Historical Center.
Otto Pieper. Interview, 1977., 1647-1B4-S650, Box: 1-S628-S630-S649-S650-S651. Southwest Minnesota Historical Center. https://smsu.libraryhost.com/repositories/3/resources/96 Accessed January 15, 2026.