BRIEF [O.A.] Bliemeister, W... Author: Bliemeister, W... Recipient: Haeckel, Ernst Dating: 18.02.1914
BRIEF [O.A.] Sprenger, Therese; Sprenger, Gustav Author: Sprenger, Therese; Sprenger, Gustav Recipient: Haeckel, Ernst Dating: 15.02.1916
TELEGRAMM Sprenger, Gustav; Sprenger Therese Author: Sprenger, Gustav; Sprenger Therese Recipient: Haeckel, Ernst Dating: 16.02.1913
TELEGRAMM Sprenger, Gustav; Sprenger, Therese Author: Sprenger, Gustav; Sprenger, Therese Recipient: Haeckel, Ernst Dating: 04.05.1915
BRIEF [O.A.] Sprenger, Therese Author: Sprenger, Therese Recipient: Haeckel, Ernst Dating: 15.02.1915