1. Baker, John Gilbert. 1903. Geographical Distribution of Vegetation in Yorkshire, by Dr. W.G. Smith. The Naturalist, June 1903: 221–223.
2. Bauer, Juliette. 1852. Lives of the Brothers Humboldt. Translated by Juliette Bauer from Philipp Klencke and Hermann Friedrich. London: Ingram, Cooke and Co.
3. Blackman, F.F., and Arthur G. Tansley. 1905. Ecology in its Physiological and Phytotopographical Aspects: Research Methods in Ecology, by F. E. Clements. New Phytologist 4 (9): 199–203.
4. Clements, Frederic E. 1904. The Development and Structure of Vegetation. Vol. 7. Studies in the Vegetation of the State, Botanical Survey of Nebraska. Lincoln, Nebraska: University of Nebraska.
5. Conard, H. S. 1951. ‘Foreword’, in Kerner von Marilaun, A. and Conard, H.S. (ed.) 1951. The background of plant ecology. Ames: Iowa State College Press.