Extensive correspondence present between Schaefer and between Shuji Tachikawa, Norihiro Ueshimo, Jospeh Vagvolgyi, Jitka Vilimova (formerly Jitka Davidova), Michael Wall, Alfred G. Wheeler, Klaus Wolf, Thomas K. Wood, Thomas E. Woodward, Thomas R. Yonke, Herbert Zettel, and Zheng Le-yi.