BRIEF [O.A.] Gjurakitsch, Wladimir Author: Gjurakitsch, Wladimir Recipient: Haeckel, Ernst Dating: 15.12.1917
BRIEF [O.A.] Julien, Pierre Author: Julien, Pierre Recipient: Haeckel, Ernst Corporation: Association Générale des Étudiants de Paris, Reconnue d'utilité publique Dating: 01.03.1907
BRIEF [O.A.] Beneden, Eduard van Author: Beneden, Eduard van Recipient: Haeckel, Ernst Dating: 11.07.1871
BRIEF [O.A.] Beneden, Eduard van Author: Beneden, Eduard van Recipient: Haeckel, Ernst Dating: 27.07.1871
BRIEF [O.A.] Beneden, Eduard van Author: Beneden, Eduard van Recipient: Haeckel, Ernst Dating: 08.09.1871
BRIEF [O.A.] Beneden, Eduard van Author: Beneden, Eduard van Recipient: Haeckel, Ernst Dating: 02.06.1872