List of sources:
FamilySearch: Christopher Toombs. https://ancestors.familysearch.org/en/G3DM-LST/christopher-toombs-1879-1952 AND https://www.familysearch.org/ark:/61903/3:1:3Q9M-C91L-XQKM-T?view=index&personArk=/ark:/61903/1:1:8SHC-ZLN2&action=view&cc=2721608&lang=en&groupId=M96N-D7W
Journal of the Chemical, Metallurgical and Mining Society of South Africa, 1906/7, Vol. 7; 1913/4, Vol. 14.
Journal of the South African Chemical Institute: First decennial index, Volumes I to X , 1918-1927.
National Archives Repository (TAB), Source MHG, Vol. 0, Ref. 4274/53: death notice, Christopher Toombs.
Schyjf, B. An historical overview of the South African Institute of Assayers and Analysts, 1919-1992. Analytica, 1994, Vol. 2(1), pp. 8-30.
South African Chemical Institute. Proceedings and list of members, 1921-1922 and 1933-1934.