BRIEF OHNE UMSCHLAG Mulder, Lodewijk Author: Mulder, Lodewijk Recipient: Haeckel, Ernst Dating: 15.02.1894
BRIEF OHNE UMSCHLAG Scheffauer, Herman Author: Scheffauer, Herman Recipient: Haeckel, Ernst Dating: 09.05.1915
BRIEF OHNE UMSCHLAG Bos-Vernet, Clara Author: Bos-Vernet, Clara Recipient: Haeckel, Ernst Dating: 11.08.1903
BRIEF OHNE UMSCHLAG Mulder, J. A., de Villeneuve Author: Mulder, J. A., de Villeneuve Recipient: Haeckel, Ernst Dating: 14.05.1907
BRIEF OHNE UMSCHLAG Treub, Melchior Author: Treub, Melchior Recipient: Haeckel, Ernst Dating: 31.07.1902
