WIA GC/10780 | Warburg, Aby to Internationales Institut für Sozial-Bibliographie 12/12/1907 | his brother Felix M. Warburg pays a membership fee of M. 25.-, Warburg pays the fee of M. 15... |
WIA GC/8486 | Warburg, Aby to Beck, Hermann 17/12/1912 | only catalogues dealing with sociology to be sent to him; regrets that they discontinued... |