BRIEF MIT UMSCHLAG Haeckel, Ingeborg Author: Haeckel, Ingeborg Recipient: Mentz, Frida Dating: 12.11.1927
BRIEF OHNE UMSCHLAG Haeckel, Ingeborg Author: Haeckel, Ingeborg Recipient: Mentz, Frida Dating: 05.12.1926
BRIEF OHNE UMSCHLAG Haeckel, Ingeborg Author: Haeckel, Ingeborg Recipient: Mentz, Frida Dating: 05.01.1930
BRIEF [O.A.] Haeckel, Ingeborg Author: Haeckel, Ingeborg Recipient: Haeckel, Ernst Dating: 25.03.1918
BRIEF [O.A.] Haeckel, Ingeborg Author: Haeckel, Ingeborg Recipient: Haeckel, Ernst Dating: 09.11.1913
BRIEF [O.A.] Haeckel, Ingeborg Author: Haeckel, Ingeborg Recipient: Haeckel, Ernst Dating: 15.02.1916