Walters, S. M. & Dandy, J. E. Flora Europaea (Tutin, T. G. et al.) 5, 6-7 (Cambridge University Press, 1980).

Reveal, J. L. Intermountain Flora - Vascular Plants of the Intermountain West, U.S.A. (Holmgren, A. H., Holmgren, N. H., Reveal, J. L. & Holmgren, P. K.) 6, 18-22 (Columbia University Press, 1977).

Munz, P. A. & Keck, D. D. A California Flora 1320-1322 (University of California Press, 1968).

Fedchenko, B. A. Flora of the U.S.S.R. 1, 216-218 (Israel Program for Scientific Translation, 1968).

Buchenau, F. Das Pflanzenreich 4, 14, 1-20 (1903).

Bolkhovskikh, Z., Grif, V., Matvejeva, T. & Zakharyeva, O. Chromosome numbers of flowering plants 361-362 (Academy of Sciences of the USSR, V.L. Komarov Botanical Institute, 1969).