Higuchi et. al, "Inhibition of Hydrolysis of Esters in Solution by Formation of Complexes. II. Stabilization of Procaine with Caffeine,", 1956

Higuchi et. al, "Inhibition of Hydrolysis of Esters in Solution by Formation of Complexes. II. Stabilization of Procaine with Caffeine,", 1956, Box: 10, Folder: 167. Personal papers of Takeru Higuchi, PP 359. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/124591 Accessed December 25, 2025.