Stubbendieck, J.; Flessner, T.R.; Weedon, R.R. 1989. Blowouts in the Nebraska Sandhills: The habitat of Penstemon haydenii. In: Bragg, T.B.; Stubbendieck, J., eds. Prairie pioneers: Ecology, history and culture: Proceedings, 11th North American Prairie Conference. 1988 August 7-11; Lincoln, NE; Lincoln, NE: University of Nebraska: 223-225.
Stubbendieck, J.; Flessner, T.R.; Weedon, R.R. 1989. Blowouts in the Nebraska Sandhills: The habitat of Penstemon haydenii. In: Bragg, T.B.; Stubbendieck, J., eds. Prairie pioneers: Ecology, history and culture: Proceedings, 11th North American Prairie Conference. 1988 August 7-11; Lincoln, NE; Lincoln, NE: University of Nebraska: 223-225.