BRIEF [O.A.] Frohwein, U... Author: Frohwein, U... Recipient: Haeckel, Ernst Corporation: Bibliographisches Institut Dating: 08.05.1912
BRIEF [O.A.] Melliess, W... Author: Melliess, W... Recipient: Haeckel, Walter Corporation: Bibliographisches Institut Dating: 18.02.1921
BRIEF [O.A.] Meyer Author: Meyer Recipient: Haeckel, Ernst Corporation: Bibliographisches Institut Dating: 27.11.1889
BRIEF [O.A.] Meyer Author: Meyer Recipient: Haeckel, Ernst Corporation: Bibliographisches Institut Dating: 06.09.1890
BRIEF [O.A.] Meyer Author: Meyer Recipient: Haeckel, Ernst Corporation: Bibliographisches Institut Dating: 21.03.1890
BRIEF [O.A.] Meyer Author: Meyer Recipient: Haeckel, Ernst Corporation: Bibliographisches Institut Dating: 16.11.1893