1. Abbott, R J, Ashton, P A, and Forbes, D G. 1992. Introgressive origin of the radiate groundsel, Senecio vulgaris L. var hibernicus Syme: AAT-3 evidence. Heredity, (in press).
2. Ashton, P A. 1990. Multiple Origins of Senecio cambrensis Rosser, and Related Evolutionary Studies in British Senecio. Ph.D. Thesis, University of St Andrews.
3. Brummitt, J M. 1971. In plant records. Watsonia, 8, 408.
4. Brettell, R I S, and Leslie, A C. 1978. Senecio squalidus L. × S. vulgaris L. in Cambridgeshire. Watsonia, 12, 155.
5. Crisp, P C. 1972. Cytotaxonomic Studies in the Section Annui of Senecio. Unpublished Ph.D. Thesis, University of London.