WIA GC 1930/1407 | KBW to Hartz, Otto 01/04/1930 | |
WIA GC/14709 | Hartz, Otto to Warburg, Aby 26/11/1924 | thanks him for the invitation to the lecture on 29 November; congratulates him on his return to... |
WIA GC/14710 | Hartz, Otto to Warburg, Aby 31/12/1924 | New Year greetings and good wishes; thanks him for copies of 'Vorträge'; also the librarian of... |
WIA GC/17557 | Warburg, Aby to Hartz, Otto 08/03/1926 | is pleased that he will attend a gathering; asks him to bring his son; he has also invited Hans... |
WIA GC/17558 | Hartz, Otto to Warburg, Aby 11/06/1926 | sends birthday greetings |