| Titel | ISBN-13 (ISBN-10) | Erschei- nungsjahr | andere Autoren |
|---|---|---|---|
| Illustrated Handbook of Succulent Plants: Asclepiadaceae | 978-3-540-41964-8 (3-540-41964-0) | 2002 | Focke Albers |
| The Genus Duvalia (Stapelieae). Stem-Succulents between the Cape and Arabia (Plant Systematics and Evolution - Supplementa SUPL 10) | 978-3-211-82984-4 (3-211-82984-9) | 1997 | |
| The Genus Duvalia : Stem-Succulents between the Cape and Arabia | 978-3-211-82983-7 (3-211-82983-0) | 1997 | |