Abbott, R., Brennan, A., James, J., Forbes, D., Hegarty, M., & Hiscock, S. (2009). Recent hybrid origin and invasion in the British Isles by a self-incompatible species, Oxford ragwort (Senecio squalidus L., Asteraceae). Biological Invasions, 11(5), 1145-1158. https://doi.org/10.1007/s10530-008-9382-3