1. Mandelbrot B B: ‘The fractal geometry of nature’, Freeman, New York (1982).
2. Rényi A: ‘Probability theory’, North-Holland, Amsterdam (1970).
3. Arlinghaus S L: ‘Fractals take a central place’, Geografiska Annaler, 67B, pp 83–88 (1985).
4. Christaller W: ‘Central places in southern Germany’, New Jersey: Englewood Cliffs (1966).
5. Batty M: ‘Cities as fractals: simulating growth and form’, in ‘Fractals and Chaos’, pp 43–49, Springer-Verlag (1991).