BRIEF [O.A.] Arnot, Raymond H... Author: Arnot, Raymond H... Recipient: Haeckel, Ernst Dating: 14.02.1906
BRIEF [O.A.] Dugan, Thomas Author: Dugan, Thomas Recipient: Haeckel, Ernst Corporation: John E. Dugan, Plumbing, Roofing and Haeting, Stoves and Gas Fixtures Dating: 28.01.1906
BRIEF [O.A.] Rüdemann, Rudolf Author: Rüdemann, Rudolf Recipient: Haeckel, Ernst Corporation: New York State Education Department Dating: 14.11.1906