BRIEF [O.A.] Lindhagen, D... G... Author: Lindhagen, D... G... Recipient: Haeckel, Ernst Corporation: Académie Royale des Sciences Dating: 06.01.1883
BRIEF [O.A.] Leche, Wilhelm Author: Leche, Wilhelm Recipient: Haeckel, Ernst Corporation: Zootomiska Institut Dating: 03.02.1911
BRIEF [O.A.] Chelius, Gustaf Author: Chelius, Gustaf Recipient: Haeckel, Ernst Corporation: Kammanditbolaget Chelius & Co., Bokförlag Dating: 06.03.1906
BRIEF [O.A.] Kögman, Ernst Author: Kögman, Ernst Recipient: Haeckel, Ernst Corporation: Idun Dating: 07.06.1919