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2. The American species of Crepis.;Babcock;Carnegie Inst. Washington Publ.,1938
3. Pleistocene biogeography of temperate deciduous forests;Davis;Geosci. Man,1976
4. Chromosome numbers of flowering plants;Federov,1969
5. Apomixis in higher plants;Gustafsson;Acta Univ. Lund. Kungl. Fysiogr. Sallsk. Handl. N. R. Avd.,1947