1. Davis, P. H. — 1975. Flora of Turkey Vol. 5 Compositae (P. Davis,ed.). —University Press, Edinburgh 890 pp.
2. Dostal, J. — 1976. Vol. 4, 138.Centaurea in Flora Europaea (T. G. Tutin, V. H. Heywood, N. A. Burges, D. M. Moore, D. H. Valentine, S. M. Walters &D. A. Webb,eds.). —Cambridge Univ. Press, Cambridge.
3. Goeden, R. D. — 1983. Critique and Revision of Harris' Scoring System for the Selection of Insect Agents in Biological Control of Weeds. —Prot. Entomol., 5, 287–301.
4. Harris, P. — 1973. The Selection of Effective Agents for the Biological Control of Weeds. —Can. Entomol., 105, 1495–1503.
5. Harris, P. — 1977. Establishment, increase and spread ofU. affinis andU. quadrifasciata in BC. —Proc. knapweed Symposium, Kanloops, BC. British Columbia Plant Science Lead Committee. (Meyers J., ed.). —Univ. of British Columbia, Vancouver BC. pp. 222–238.