Aurich, C. & Podlech, D. 1989: Zur Gliederung von Asteriscus spinosus (L.) Schultz Bip. sensu lato (Compositae). – Mitt. Bot. Staatssamml. München 28: 239-296
but names used differing
1
Tubes of ligular flowers 0.5-0.8(-1.0) mm long; longest bracts mostly 3-4 times longer than ligular flowers
