Lawder, Margaret (January 1966). "The Farmer and the Flora". Journal of the Botanical Society of South Africa. 52 (1): 26. ISSN0042-3203. Retrieved 14 February 2019.
jstor.org
"Work in Progress". Quarterly Newsletter. 4 (4). Garden History Society: 14–16. Spring 1967. JSTOR1586179.
Lawder, Margaret (January 1966). "The Farmer and the Flora". Journal of the Botanical Society of South Africa. 52 (1): 26. ISSN0042-3203. Retrieved 14 February 2019.