List of sources:
Bullock, A.A. Bibliography of South African botany (up to 1951). Pretoria: Department of Agricultural Technical Services, 1978.
Gunn, M. & Codd, L.E. Botanical exploration of southern Africa. Cape Town: Balkema, 1981.
Hall, A.L. Bibliography of South African geology to the end of 1920. Pretoria: Geological Survey, Memoir No. 18, 1922.
Hillebrecht, W. Unpublished notes for a Dictionary of Namibian biography. Windhoek: National Archives of Namibia, June 2004.
Hugo, P.J., Schalk, K.E.L. & Barnes, S.J. Bibliography of South West African/Namibian earth science. Windhoek: Geological Survey, 1983.
Kienetz, A. Nineteenth-century South West Africa as a German settlement colony (pp. 417-431). PhD thesis in social geography, University of Minnesota, 1976. Facsimile by University Microfilms International, Ann Arbor, Michigan, 1977.
Logan, R.F. Bibliography of South West Africa, geography and related fields. Windhoek: South West Africa Scientific Society, 1969.
National Union Catalogue, pre-1956 imprints. London: Mansell, 1968-1980.