BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Haeckel, Charlotte Dating: 05.04.1873
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Haeckel, Charlotte Dating: 18.04.1873
BRIEF [O.A.] Constant, C... Author: Constant, C... Recipient: Haeckel, Ernst Corporation: Propagande Scientifique en Orient Dating: 09.08.1878