P.  Sell and Murrell, G., Flora of Great Britain and Ireland. Vol. 4 Campanulaceae _ Asteraceae. Cambridge University Press, Cambridge: XXVIII, 2006.

P.  Sell and Murrell, G., Flora of Great Britain and Ireland. Vol. 3 Mimosaceae _ Lentibulariaceae. Cambridge University Press, Cambridge: XXVIII, 2009.

P. D.  Sell and Murrell, G., Flora of Great Britain and Ireland. Vol. 5. Cambridge: Cambridge University Press, 1996.