Moore, L. B. & Edgar, E. Flora of New Zealand 2, 7-8 (A.R. Shearer, 1970).

Britton, N. & Brown, A. Flora of the Northern United States and Canada 1, 91-93 (Dover Publications, 1970).

Burbidge, N. T. & Gray, M. Flora of the Australian Capital Territory (Australian National University Press, 1970).