List of sources:
De Volkstem, 2 October 1875, p. 2, De Botanische Tuin; 13 June 1877, p. 2, Invoer van planten, zaden, enz.; 27 June 1877, p. 2, The proposed botanical gardens.
FamilySearch: Otto Linke. https://www.familysearch.org/ark:/61903/3:1:3Q9M-CS4F-VYX7?view=index&personArk=/ark:/61903/1:1:QPTX-JQXN&action=view&cc=2520237&lang=en
Gunn, M. & Codd, L.E. Botanical exploration of southern Africa. Cape Town: Balkema, 1981.
Jeppe, F. Transvaal book almanac and directory for 1877 (pp. 59, 83). Pietermaritzburg: P. Davis & Sons, 1877 (Reprint No. 80, The State Library, Pretoria, 1976).
National Archives Repository (TAB), Vol. SS222, Ref. R3531/76, letter from Lincke to State Secretary, 12 December 1876; Vol. SS237, R1677/77, 30 April 1877 and SS237, R2034/77, 28 May 1877, D.M. Kisch and others to acting State Secretary; Vol. SS237, R1941/77, 22 May 1877, Lincke to acting State Secretary.
National Automated Archival Information Retrieval System (NAAIRS). http://www.national.archives.gov.za/naairs.htm Documents relating to Lincke, O. / Lincke, A. / Linke, Otto / Lindke, O. / Lindke.
Staats-Courant der Zuid-Afrikaansche Republiek (Government Gazette), 5 Januari 1876, p. 16, Gouvernements Kennisgeving No. 2; 9 June 1877, p. 61, Government Notice No. 51; 2 December 1879, p. 453, Notice.