Ernest Horn thesis, "An experiment in the seventh grade of the teachers college elementary school, University of Missouri, in an attempt to find a principle which would remedy some of the defects of the present elementary school curriculum," Final draft, original, 1908, Box: 34. Ernest Horn Papers, RG99.0223. University of Iowa Archives. https://aspace.lib.uiowa.edu/repositories/3/archival_objects/1158079 Accessed February 24, 2025.