Pterocephalus perennis subsp. perennis

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1976, Flora Europaea. Volume 4. Plantaginaceae to Compositae (and Rubiaceae), Cambridge University Press : 68

(a) Subsp. perennis ( P. perennis subsp. parnassi (Sprengel) Vierh. ): Leaves more or less densely grey-pubescent or -tomentose, usually sparsely glandular, the veins on the lower surface hidden. 5. & E. Greece.