Higuchi et. al, "Prodrugs of 6-Thiopurines: Enhanced Delivery Through the Skin,", 1983, Box: 11, Folder: 67. Personal papers of Takeru Higuchi, PP 359. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/124701 Accessed January 02, 2025.