References:

1. Campbell, F. T., ed. Report of National Coalition of Exotic Plant Pest Councils. 1995 (unpublished draft) (Rep NCEPPC)
2. Conant, P. et al. 1997. Appendix. Selected plant species interfering with resource management goals in North American natural areas (Pl Invasion) 255-267.
3. Davis, P. H., ed. Flora of Turkey and the east Aegean islands. (F Turk)
4. Gleason, H. A. & A. Cronquist Manual of vascular plants of northeastern United States and adjacent Canada. (Glea Cron)
5. Komarov, V. L. et al., eds. Flora SSSR. (F USSR)
6. Liberty Hyde Bailey Hortorium Hortus third. (Hortus 3)
7. Martin, W. C. & C. R. Hutchins A flora of New Mexico. (F New Mex)
8. Ochsmann, J. 2000. Morphologische und molekularsystematische Untersuchungen an der Centaurea stoebe L.-Gruppe (Asteraceae-Cardueae) in Europa Diss. Bot. 324:70.
9. Ochsmann, J. 2001. On the taxonomy of spotted knapweed (Centaurea stoebe L.) (Proc Knapweed Symp) 38.
10. Radford, A. E. et al. Manual of the vascular flora of the Carolinas. (F Carolin)
11. Radford, A. E. et al., eds. Vascular flora of the southeastern United States. (F SE US)
12. Scoggan, H. J. The flora of Canada, 4 vol. (F Canada)
13. Seed Regulatory and Testing Division, Agricultural Marketing Service, U.S.D.A. State noxious-weed seed requirements recognized in the administration of the Federal Seed Act (updated annually). (State Noxweed Seed)
14. Steyermark, J. A. Flora of Missouri. (F Missouri)
15. Tutin, T. G. et al., eds. Flora europaea. (F Eur)

Images:

• Fruits: U.S. National Seed Herbarium image