BRIEF [O.A.] Thoden van Velzen, S... K... Author: Thoden van Velzen, S... K... Recipient: Haeckel, Ernst Dating: 03.07.1912
BRIEF [O.A.] Thoden van Velzen, S... K... Author: Thoden van Velzen, S... K... Recipient: Haeckel, Ernst Dating: 05.08.1912
BRIEF [O.A.] Thoden van Velzen, S... K... Author: Thoden van Velzen, S... K... Recipient: Haeckel, Ernst Dating: 16.08.1912
BRIEF [O.A.] Thoden van Velzen, S... K... Author: Thoden van Velzen, S... K... Recipient: Haeckel, Ernst Dating: 12.12.1912