J. M.  Gillett and Robson, N. K. B., The St. John's-wort of Canada (Guttiferae). Ottawa: National Museums of Canada, 1981, p. iv, 40p.- illus., maps, chrom. nos., keys.

S. I.  Ali, Flora of Libya: 2. Guttiferae. Tripoli: Al Faateh University, 1976, p. 10p. -   Illus., map, key.

N. K. B.  Robson, Flora of West Pakistan: no. 32. Guttiferae. 1973, p. 12p.

R.  C Jimenez, Recherches sur le genre Hypericum L. section Brathys (Mutis ex L.f.) Choisy sous-section Spachium Keller (Guttiferae) These. (s.l.), 1973, p. 139p.

P.  Bamps, Guttiferae: 60-76. Distrib. Pl. Afr., 1971, p. 3. 17p.(1971).

N. K. B.  Robson, Studies in the genus Hypericum L. (Guttiferae): 3. Sections: 1. Campylosporus to: 6a. Umbraculoides., vol. 12. Bull. Brit. Mus. (Nat. Hist.) Bot., 1985, p. 325p. (1985) - illus., maps, chrom. nos., keys.