- A new variety of Haworthia Limifolia from Natal (1962)
- Haworthia as a problem genus (1970)
- Variation in Haworthia with particular reference to HAWORTHIA GLAUCA, Baker. (1970)
- Changes in the genus Haworthia Duval (1971)
- Anguish Among the Haworthias. (1972)
- Natural Variation and Species Delimitation in Haworthia Duval. – Part 1. HAWORTHIA RETICULATA (Haw.) Haworth (1972)
- Natural Variation and Species Delimitation in Haworthia Duval. – Part 2. HAWORTHIA HERBACEA (Miller) Stearn. (1972)
- Reinstatement of the Genera Astroloba and Poellnitzia Uitew.
- Natural Variation and Species Delimitation in Haworthia Duval. – Part 3. HAWORTHIA REINWARDTII Haw. and HAWORTHIA COARCTATA Haw. (1973)
- Leaf spirals in Haworthia. (1973)
- New Haworthia (1974)
- Name Changes in Haworthia Concerning H. Obtusa Haw. and H. Pilifera Bak.
- Haworthias – small relatives of Aloe (1974)
- Haworthia Duval: Section Retusae fide Scott — Additional Comment (1974)
- The ‘Retuse’ Haworthias (1975)
- Haworthia mirabilis Haworth. (1977)
- Natural Variation and Species Delimitation in Haworthia Duval. – Part 4. HAWORTHIA EMELYAE von Poelln. and a new variety. (1979)
- A Story of Haworthia Nitidula v. Poelln. (= H. mirabilis Haw.) (1980)
- Looking for Haworthias (1980)
- Natural Variation and Species Delimitation in Haworthia Duval. – Part 5. HAWORTHIA ANGUSTIFOLIA Haworth. (1981)
- Observations on the G.G. Smith Collection of Haworthia (1982)
- The Cape Flora and the Karoo (1984)
- Haworthia – Confusion Reigns Again (1986)
- Haworthia and Nomenclatural Confusion (1987)
- Natural Variation and Species Delimitation in Haworthia Duval. – Part 6. HAWORTHIA MACULATA (v. Poelln.) Bayer. (1987)
- Haworthia History – Zurich (1997)
- Fundamentals as I see them (1997)
- Gravitational collapse and black holes in Haworthia (1997)
- Haworthia cymbiformis var. reddii (Scott) Bayer – a test of an hypothesis. (1997)
- Factual information about BB
- Haworthia, why controversy?
- Beware of the dog (1999)
- A shadow of the past – Haworthia arachnoidea again. (1999)
- The intractable problem of look-alikes in Haworthia. (2001)
- Haworthiad Letters (1988–1998)
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