Henry Morton Stanley: In darkest Africa. Volume II. New York, 1890, S. 1–540 (S. 490) ([1])
Harry Hamilton Johnston: The Okapi. In: C. J. Corner, F. C. Selous, H. Johnston, C. H. Lane, L. Wain, W. P. Pycraft, H. A. Byden, F. G. Aflalo und W. Saville-Kent (Hrsg.): The living animals of the world. London, 1901, S. 267–270 ([3])
biodiversitylibrary.org
Harry Hamilton Johnston: On a new horse. Proceedings of the Zoological Society of London 1900, S. 774–775 ([2])
Philip Lutley Sclater: On an apparently new Zebra from the Semliki forest. Proceedings of the Zoological Society of London 1901, S. 50–52 ([4])
E. Ray Lankester: Two skulls and the skin of the new mammal, the Okapi, discovered by Sir Harry Johnston. Proceedings of the Zoological Society of London 1901, S. 279–281 ([5])
E. Ray Lankester: On Okapia, a new genus of Giraffidae, from Central Africa. Proceedings of the Zoological Society of London 1901, S. 472–474 ([6])
E. Ray Lankester: On Okapia, a new genus of Giraffidae, from Central Africa. Transactions of the Zoological Society of London 1902/1903, S. 279–314 ([7])