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2. On the existence of two forms, and on their reciprocal sexual relation, in the several species of the genus Linum;Darwin;J. Linn. Soc. Bot.,1864
3. Pollen Morphology and Plant Taxonomy;Erdtman,1952
4. An introduction to a Scandinavian pollen flora;Erdtman;Grana Palynol.,1961
5. Textbook of Pollen Analysis;Faegri,1975