BRIEF [O.A.] Krauseneck, Valentine Author: Krauseneck, Valentine Recipient: Haeckel, Ernst Dating: 14.03.1906
BRIEF [O.A.] Krauseneck, Valentine Author: Krauseneck, Valentine Recipient: Haeckel, Ernst Dating: 26.12.1906
BRIEF OHNE UMSCHLAG Krauseneck, Gustav Adolf Author: Krauseneck, Gustav Adolf Recipient: Haeckel, Ernst Dating: 22.11.1906
ANSICHTSKARTE Krauseneck, Gustav Adolf Author: Krauseneck, Gustav Adolf Recipient: Haeckel, Ernst Dating: 29.12.1906