References

For Helenium

Bierner, M.W. 1972. Taxonomy of Helenium sect. Tetrodus and a conspectus of North American Helenium (Compositae). Brittonia 24: 331-355. Google Scholar

Bierner, M.W. 1989. Taxonomy of Helenium sect. Amarum (Asteraceae). Sida 13: 453-459. Google Scholar

Bierner, M.W. 2006b. Helenium. In Flora of North America Editorial Committee. 2006c. Flora of North America north of Mexico. Volume 21, Magnoliophyta: Asteridae, part 6: Asteraceae, part 3. Oxford Univ. Press, New York, NY. 616 pp. Google Scholar

Cronquist, A. 1980. Asteraceae, Volume I, Vascular flora of the Southeastern United States. University of North Carolina Press, Chapel Hill, N.C. Google Scholar

Fernald, M.L. 1943. Virginian botanizing under restrictions. Rhodora 45: 357-511 (pagination interrupted). Google Scholar

Knox, J.S. 1987. An experimental garden test of characters used to distinguish Helenium virginicum Blake from H. autumnale L. Castanea 52: 52-58. Google Scholar

Knox, J.S., K. Bezold, P.R. Cabe, S. Williams, and M.C. Simurda. 2016. Genetic diversity and population structure of the endemic disjunct species, Helenium virginicum (Asteraceae). Amer. Midland Naturalist 175 242-260. Google Scholar

Rock, H.F.L. 1957. A revision of the vernal species of Helenium (Compositae). Rhodora 59: 101-116, 128-159, 168-178, 203-216. Google Scholar

Rydberg, P.A. 1915. Carduales. Carduaceae. Heleniae, Tageteae. North American Flora 34, Part 2: 81-180. Google Scholar