1. Allen, P., 1991 Spatial models of evolutionary systems, in Spatial analysis and population dynamics, D. Pumain, ed., John Libbey-INED, Congresses and Colloquia 6, Paris.
2. Allen, P., and Sanglier, M., 1979, A dynamic model of growth in a central place system, Geographical Analysis. 2: 256–272.
3. Alperovich, G., 1993, An explanatory Model of City-size distribution: Evidence from Crosscountry Data, Urban Studies. 9: 1591–1601.
4. Amson, J.C., 1972, Equilibrium models of cities, an axiomatic theory, Environment and Planning A. 4: 429–44.
5. Anderson, C., Hellervik, A., Hagson, A,. and Tornberg, J., 2003, The urban economy as a scale-free network. ArXiv:cond-mat/0303535 v2.