BRIEF OHNE UMSCHLAG Bail; Conwentz Author: Bail; Conwentz Recipient: Haeckel, Ernst Corporation: Naturforschende Gesellschaft zu Danzig Dating: 18.12.1889
TELEGRAMM Recipient: Haeckel, Ernst Corporation: Naturforschende Gesellschaft zu Danzig Dating: 16.02.1894
BRIEF [O.A.] Jacobsohn, J... H... Author: Jacobsohn, J... H... Recipient: Haeckel, Ernst Corporation: Papiergrosshandlung – Exporthaus Dating: 27.01.1914