Lactuca quercina subsp. quercina

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 : 330

(a) Subsp. quercina ( L. stricta Waldst. & Kit. , L. quercina subsp. stricta (Waldst. & Kit.) Hayek ): Beak of achene less than 2-4 mm. 2л = 18. Woods and scrub', nitrophile. Throughout the range of the species.