Higuchi and Rehm, "Extrapolation Plot for Photometric Titration of Weak Bases in Aqueous and Nonaqueous Systems,", 1957, Box: 10, Folder: 136. Personal papers of Takeru Higuchi, PP 359. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/124560 Accessed May 25, 2024.