BRIEF OHNE UMSCHLAG Bauer, Karl; Bauer Klotilde Author: Bauer, Karl; Bauer Klotilde Recipient: Haeckel, Ernst Dating: 15.02.1909
BRIEF OHNE UMSCHLAG Bauer, Klotilde Author: Bauer, Klotilde Recipient: Haeckel, Ernst Dating: 03.05.1911
POSTKARTE Bauer, Karl; Bauer, Klotilde Author: Bauer, Karl; Bauer, Klotilde Recipient: Haeckel, Ernst Dating: 29.12.1911