List of sources:
Burtt-Davy, J. & Leendertz, R. First annotated catalogue of the vascular plants of the Transvaal and Swaziland. Report of the South African Association for the Advancement of Science, 1908, pp. 230-236.
FamilySearch: George Thorncroft. https://www.familysearch.org/en/tree/person/details/G8HC-QZY
Gunn, M. & Codd, L.E. Botanical exploration of southern Africa. Cape Town: Balkema, 1981.
Jessop, J.P. Some botanists and botanical collectors associated with southern Africa. Lantern, September 1963, Vol. 13(1), pp. 80-85.
National Archives Repository (TAB), Source MHG, Vol. 0, Ref. 1248/64: death notice, Joseph Norton Thorncroft.
South African Association for the Advancement of Science. Report, 1905/6, list of members.
South African Journal of Science, 1933, Vol. 30, note by Thorncroft.
Standard encyclopaedia of southern Africa (SESA). Cape Town: NASOU, 1970-1976.
Transvaal [Colony], Department of Agriculture. Report for 1903/4, pp. 206-249.
Transvaal Museum. Annual Report, 1906/7. (National Archives, Pretoria, Vol. TKP 196).
United Transvaal directory, 1926, 1927, 1933.