BRIEF [O.A.] Constan, Estouruelle de Author: Constan, Estouruelle de Recipient: Haeckel, Ernst Dating: 20.05.1905
BRIEF [O.A.] Constan, Estouruelle de Author: Constan, Estouruelle de Recipient: Haeckel, Ernst Corporation: Conciliation Internationale Dating: 11.12.1905
BRIEF [O.A.] Constan, Estouruelle de Author: Constan, Estouruelle de Recipient: Haeckel, Ernst Corporation: Sénat Dating: 14.01.1906
BRIEF [O.A.] Constan, Estouruelle de Author: Constan, Estouruelle de Recipient: Haeckel, Ernst Corporation: Sénat Dating: 23.05.1909