Brief an Professor [Adolf Dyroff]
Amsterdam, 28.08.1914 [28/VIII [19]14]Brief an Professor [Adolf Dyroff]
Amsterdam, 23.09.1914 [23/IX [19]14]Brief an Professor [Adolf Dyroff]
Amsterdam, 06.04.1915 [6/IV [19]15]Brief an Professor [Adolf Dyroff]
Amsterdam, 29.04.1915 [29/IV [19]15]Brief an Professor [Adolf Dyroff]
Amsterdam, 10.05.1918 [10/V [19]18]Brief an Professor [Adolf Dyroff]
Amsterdam, 17.06.1922 [17/VI [19]22]Brief an Professor Dyroff
Amsterdam, 1922 [[ohne Datum, 1922]]Postkarte an Professor Dr Ad Dyroff, Bonn a/Rh, Rich. Wagnerstr 7
Amsterdam, 11.08.1914 [11/VIII [19]14]