BRIEF OHNE UMSCHLAG Schwalbe, Gustav; Schwalbe, Clara Author: Schwalbe, Gustav; Schwalbe, Clara Recipient: Haeckel, Ernst Dating: 14.02.1904
BRIEF OHNE UMSCHLAG Schwalbe, Gustav Author: Schwalbe, Gustav Recipient: Haeckel, Ernst Dating: 17.10.1904
TELEGRAMM Ruge, Marcus Arnold Author: Ruge, Marcus Arnold Recipient: Haeckel, Ernst Dating: 16.02.1904