^Three variants of ecological niche are described by Thomas W. Schoener (2009). "§I.1 Ecological niche". In Simon A. Levin; Stephen R. Carpenter; H. Charles J. Godfray; Ann P. Kinzig; Michel Loreau; Jonathan B. Losos; Brian Walker; David S. Wilcove (eds.). The Princeton Guide to Ecology. Princeton University Press. pp. 3 ff. ISBN978-1-4008-3302-3.
^A Townsend Peterson; Jorge Soberôn; RG Pearson; Roger P Anderson; Enrique Martínez-Meyer; Miguel Nakamura; Miguel Bastos Araújo (2011). "Species-environment relationships". Ecological Niches and Geographic Distributions (MPB-49). Princeton University Press. p. 82. ISBN978-0-691-13688-2. See also Chapter 2: Concepts of niches, pp. 7 ff