De Marne, F.E. & Van der Walt, J.J.A. 1990. Pelargonium tomentosum: a potential source of peppermint-scented essential oil. South African Journal of Plant & Soil 7(1).
http://pza.sanbi.org/references/de-marne-fe-van-der-walt-jja-1990-pelargonium-tomentosum-potential-source-peppermint