1. Notes on some plants of Southern Africa chiefly from Natal: IX;Hilliard,1982
2. Notes on some plants of Southern Africa chiefly from Natal: X;Hilliard,1983
3. Index Herbariorum 1. The herbaria of the world;Holmgren;Regnum Vegetabile,1981
4. Phylogenetics of tribe Exaceae (Gentianaceae) based on molecular, morphological and karyological data, with special emphasis on the genus Sebaea-Taxonomic treatment of Exochaenium, Lagenias and the new genus Klackenbergia;Kissling,2007