Higuchi and Lach, "Investigation of Complexes Formed in Solution by Caffeine. V. Interactions Between Caffeine and p-Aminobenzoic Acid, m-Hydroxybenzoic Acid, Picric Acid, o-Phthalic Acid, Suberic Acid, and Valeric Acid,", 1954, Box: 10, Folder: 189. Personal papers of Takeru Higuchi, PP 359. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/124613 Accessed June 26, 2024.