1. Abler, R.F. (1987) The National Science Foundation National Center for Geographic Information and Analysis’, International Journal of Geographic Information Systems 1(4), 303–326.
2. Abler, R.F., Adams, J.S. and Gould, P.R. (1971) Spatial organization: the geographer’s view of the world, Englewood Giffs, NJ: Prentice Hall.
3. Alexandroff, P. (1961) Elementary concepts of topology, New York: Dover Publications.
4. Bartels, D. (1982) ‘Geography: Paradigmatic change or functional recovery? A view from West Germany’, in Gould, P. and Olsson, G. (eds.), A search for common ground, London; Pion.
5. Bergmann, P.G. and Sabatta, V. de (1986) (eds.) Topological properties and global structure of space-time, (Proceedings of a NATO Advanced Study Institute), New Yoik: Plenum Press.