Eckenwalder, J.E. (1980), "Foliar Heteromorphism in Populus (Salicaceae), a Source of Confusion in the Taxonomy of Tertiary Leaf! Remains", Systematic Botany, 5 (4): 366–383, doi:10.2307/2418518, JSTOR2418518{{citation}}: תחזוקה - ציטוט: שימוש בפרמטר authors (link)
jstor.org
Eckenwalder, J.E. (1980), "Foliar Heteromorphism in Populus (Salicaceae), a Source of Confusion in the Taxonomy of Tertiary Leaf! Remains", Systematic Botany, 5 (4): 366–383, doi:10.2307/2418518, JSTOR2418518{{citation}}: תחזוקה - ציטוט: שימוש בפרמטר authors (link)