BRIEF OHNE UMSCHLAG Magnussen, Harro Author: Magnussen, Harro Recipient: Haeckel, Ernst Dating: 03.04.1905
BRIEF [O.A.] Harden, Maximilian Author: Harden, Maximilian Recipient: Haeckel, Ernst Dating: 22.01.1905
BRIEF [O.A.] Harden, Maximilian Author: Harden, Maximilian Recipient: Haeckel, Ernst Dating: 06.04.1905