Gleason, Henry A. and Cronquist, Arthur, (1991), Manual of Vascular Plants of Northeastern United States and Adjacent Canada, New York Botanical Garden, Bronx, New York, pp. 839–840. – In reply to Cronquist, A. S. Weakley points out that there is “a broad suite of morphological distinctions from European C. majalis” and that C. pseudomajalis, as he calls this taxon, is typically found “on ridges remote from present or past habitations” which excludes the idea of the taxon stemming from garden escapes. – Weakley, A. S. 2020. Flora of the southeastern United States. University of North Carolina Herbarium, North Carolina Botanical Garden. p. 281 (Download page)
