BRIEF OHNE UMSCHLAG Dosenheimer, Emil Author: Dosenheimer, Emil Recipient: Haeckel, Ernst Dating: 25.02.1908
BRIEF [O.A.] Schleicher, Erh... Author: Schleicher, Erh... Recipient: Haeckel, Ernst Dating: 05.03.1899
BRIEF [O.A.] Wölfling, Friedrich Author: Wölfling, Friedrich Recipient: Haeckel, Ernst Dating: 19.09.1915
BRIEF [O.A.] Wölfling, Friedrich Author: Wölfling, Friedrich Recipient: Haeckel, Ernst Dating: 08.06.1912
TELEGRAMM Dosenheimer, Emil Author: Dosenheimer, Emil Recipient: Haeckel, Ernst Corporation: Deutscher Monistenbund, Ortsgruppe Mannheim - Ludwigshafen a. Rh. Dating: 17.02.1911