RDB

British Red Data Book, Volume 1: Vascular Plants. (1977) Society for the Promotion of Nature Conservation, Lincoln.

Fox, R., Warren, M.S. & Brereton, T.M. (2010) The Butterfly Red List For Great Britain. Joint Nature Conservation Committee, Peterborough.

Cheffings, C.M., Farrell, L., Dines, T.D., Jones, R.A., Leech, S.J., McKean, D.R., Pearman, D.A., Preston, C.D., Rumsey, F.J. & Taylor, I. (2005) The Vascular Plant Red Data List For Great Britain. Species Status No. 7. Joint Nature Conservation Committee, Peterborough.

Perring, F.H. & Farrell, L. (1983) British Red Data Book, Volume 1: Vascular Plants, 2nd ed. Royal Society for the Conservation of Nature, Lincoln.