Casas J. F. 1977: Chromosome number report., LV. -Taxon, 26 (1): 107-109.
Darlington, C. D. & Wylie, A. P. 1955: Chromosome Atlas of flowering Plants. - George Allen and Unwin Ltd. London.
Fedorov, An. A. 1969: Chromosome Number of Flowering Plants. - Komarov Botanical Institute, Leningrad.
Goldblatt P. & Dale E. 1975-1991: Index to Plant Chromosome Number. -Missouri Botanical Garden.
Moore, D. M. 1982: Flora Europae Check-list and Chromosome Index. -Cambridge Univeristy Press, London.
Rechinger, K. H. 1977: Scorzonera L. in K. H. Rechinger Flora Iranica no. 122. -Graz.
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