1. Arlinghaus, S.L.: 1993, ‘Central place fractals: theoretical geography in an urban setting’, Fractals in Geography, Lam, N.S.-N. and DeCola, L. (eds.), Prentice Hall, Englewood Cliffs, NJ, pp. 213–227.
2. Baumgardner, J.R. and Frederickson, P.O.: 1985, ‘Icosahedral discretization of the two-sphere’, SIAM Journal on Numerical Analysis 22(6), 1107–1115.
3. Bell, S.B.M., Diaz, B.M., Holroyd, F. and Jackson, M.J.: 1983, ‘Spatially referenced methods of processing raster and vector data’, Image and Vision Computing 1(4), 211–220.
4. Commission for Environmental Cooperation, 1997: Ecological Regions of North America: Toward a Common Perspective, Montreal, Canada, 71 pp.
5. Dutton, G.H.: 1998, A hierarchical coordinate system for geoprocessing and cartography, Lecture Notes in Earth Science 79, Springer-Verlag, Berlin, 231 pp.