Carduus

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 : 222

Sect. Carduus . Capitula depressed-globose to campanulate, often large and pedunculate, persistent; corolla-tube widened above into an oblong cup (2-)2-5-5 mm.