1. A. Cronquist, An Integrated System of Classification of Flowering Plants, Columbia University Press, 1981, pp.1011–1013.
2. N. Marekof, N.V. Handjieva, S. Popov, I. Jankulov, Study on the Valepotriate content in the roots of some Valeriana specie grown in Bulgaria, Commun. Dept. Chem. Bulgarian Acad. Sci. 8 (1975) 672–679.
3. T.G. Tutin, V.H. Heywood, H.A. Burges, D.M. Moore, D.H. Valentine, S.M. Walters, Flora Europaea, vol. 4, Cambridge University Press, 1976, pp. 52–55.
4. S. Pignatti, Flora d’ Italia, Edagricole, Bologna, 1997.
5. M.E. Soulè, Thresholds for survival: maintaining fitness and evolutionary potential, in: M.E. Soulè, B.A. Wilcox (Eds.), Conservation Biology: an Evolutionary-Ecological Approach, Sinauer Associates Inc., Sunderland, MA, 1980, pp. 151–169.