1. Schlich's. 1910.“Manual of Forestry,”,, 4th ed. Vol. II, 287 Silviculture, p
2. Private papers.
3. P. insignis (Doug.) in South Africa.” Bull. 15 of the Forest Department of South Africa18–19. Pretoria, S.A.
4. Schlich's.“Manual of Forestry,”Vol. II, 284–5.