Verbatim text: Rock, H. F. L. 1957. A revision of the vernal species of Helenium (Compositae). Rhodora 59: 101–116, 128–158, 168–178, 203–216.
Author: Rock, H.F.L.
Year: 1957
Title: A revision of the vernal species of Helenium (Compositae)
Journal: Rhodora
Volume: 59
Pages: 101–116, 128–158, 168–178, 203–216