BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 27.11.1893
BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 16.02.1894
BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 11.07.1894
POSTKARTE Wang, Ludwig; Opper, ? Author: Wang, Ludwig; Opper, ? Recipient: Haeckel, Ernst Dating: 06.02.1907
BRIEF [O.A.] Pieper Author: Pieper Recipient: Haeckel, Ernst Corporation: Agentur des Norddeutschen Lloyd Dating: 06.10.1900
BRIEF OHNE UMSCHLAG Muller, Johan Author: Muller, Johan Recipient: Haeckel, Ernst Corporation: Koninklijke Natuurkundige Vereeniging in Nederlandsch-Indie Dating: 11.11.1900
BRIEF OHNE UMSCHLAG Muller, Johan Author: Muller, Johan Recipient: Haeckel, Ernst Corporation: Koninklijke Natuurkundige Vereeniging in Nederlandsch-Indie Dating: 15.11.1900
BRIEF OHNE UMSCHLAG Muller, Johan Author: Muller, Johan Recipient: Haeckel, Ernst Corporation: Topographische Dienst Triangulatie Brigade Dating: 25.11.1890
BRIEF OHNE UMSCHLAG Muller, Johan Author: Muller, Johan Recipient: Haeckel, Ernst Corporation: Koninklijke Natuurkundige Vereeniging in Nederlandsch-Indie Dating: 10.12.1900