1. Elliot, Eveline. 1950. A new phase of amphiplasty in Leontodon. New Phytol, 49, 344–349.
2. Finch, R A. 1966. Chromosomal and morphological variation in the British flora. D. Phil, thesis, Oxford. (In library of Botany School, Oxford).
3. Ford, E B. 1940. Polymorphism and Taxonomy. The New Systematics, ed. Huxley, J. Clarendon Press, Oxford, 493–513.
4. Löve, A, and Löve, D. 1948. Chromosome Numbers of Northern Plant Species. Reykjavik Univ Inst App Sci Dept Agric Rep, B, 3, 133 pp.
5. McNaughton, I H, and Harper, J L. 1960. The comparative biology of closely related species living in the same area. II. Aberrant morphology and a virus-like syndrome in hybrids between Papaver rhoeas L. and P. dubium L. New Phytol, 59, 27–41. III. The nature of barriers isolating sympa trie populations of Papaver dubium and P. lecoqii. New Phytol., 59, 129–137.