BRIEF [O.A.] Krauseneck, Heinrich Author: Krauseneck, Heinrich Recipient: Haeckel, Ernst Dating: 21.01.1888
BRIEF [O.A.] Krauseneck, Heinrich Author: Krauseneck, Heinrich Recipient: Haeckel, Ernst Dating: 31.12.1888
BRIEF OHNE UMSCHLAG Kossel, Johann Author: Kossel, Johann Recipient: Haeckel, Ernst Dating: 27.11.1888