BRIEF OHNE UMSCHLAG Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Dating: 21.11.1890
BRIEF MIT UMSCHLAG Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Dating: 13.10.1891
BRIEF [O.A.] Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Corporation: Königliches Zoologisch Zootomisches Institut, Universität Marburg Dating: 12.09.1872
BRIEF OHNE UMSCHLAG Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Dating: 27.01.1877
BRIEF OHNE UMSCHLAG Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Dating: 24.05.1879
BRIEF OHNE UMSCHLAG Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Dating: 22.11.1889