BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Strasburger, Eduard Dating: 01.12.1899
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Strasburger, Eduard Dating: 01.03.1904
BRIEF MIT UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Strasburger, Eduard Dating: 05.04.1910
BRIEF MIT UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Strasburger, Eduard Dating: 10.06.1910
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Strasburger, Eduard Dating: 08.11.1882