BRIEF OHNE UMSCHLAG Geheeb, Adalbert Author: Geheeb, Adalbert Recipient: Haeckel, Ernst Dating: 08.12.1905
POSTKARTE Wiedersheim, Robert Author: Wiedersheim, Robert Recipient: Haeckel, Ernst Dating: 02.07.1905
BRIEF [O.A.] Steiner, G... Author: Steiner, G... Recipient: Haeckel, Ernst Corporation: Geologisches Institut Dating: 08.03.1905