BRIEF OHNE UMSCHLAG Beneden, Eduard van Author: Beneden, Eduard van Recipient: Haeckel, Ernst Dating: 03.01.1891
BRIEF [O.A.] Van Bambeke, Charles Author: Van Bambeke, Charles Recipient: Haeckel, Ernst Dating: 15.11.1891
BRIEF [O.A.] Beneden, Eduard van Author: Beneden, Eduard van Recipient: Haeckel, Ernst Dating: 15.01.1891