Higuchi and Guttman, "Reversible Association of Caffeine and of Some Caffeine Homologs in Aqueous Solution,", 1957, Box: 11, Folder: 86. Personal papers of Takeru Higuchi, PP 359. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/124720 Accessed January 02, 2025.