BioStor
 | An Analysis of the Flora of Southern Africa: Its Characteristics, Relationships, and Orgins Peter Goldblati (1978) Annals of the Missouri Botanical Garden 65: 369-436 |
 | Chemosystematic Notes on the Asteraceae II. Acyclic Sesquiterpenes F Bohlmann, R M King and H Robinson (1979) Phytologia 41: 387-395 |
 | The genera of Cardueae (Compositae; Asteraceae) in the southeastern United States R W Scott (1990) Journal of the Arnold Arboretum 71: 391-451 |