Verbatim text: Bierner, M. W. 1972. Taxonomy of Helenium sect. Tetrodus and a conspectus of North American Helenium (Compositae). Brittonia 24: 331–355.
Author: Bierner, M.W.
Year: 1972
Title: Taxonomy of Helenium sect. Tetrodus and a conspectus of North American Helenium (Compositae)
Journal: Brittonia
Volume: 24
Pages: 331–355