1. Madden, C.H., On some indications of stability in the growth of cities in the United States, Economic Development and Cultural Change, 1956, p. 242.
2. The numbers in fig.4.2 are in accord with fig.4.1 and will be used in this way in the rest of this chapter.
3. Smith, R.H.T., Method and purpose in functional town classification, Annals of the Association of American Geographers, 1965, Vol. 55, pp. 539–548.
4. Smith, R.H.T.,op. cit. 3, p.541.
5. Steigenga, W., A comparative analysis and a classification of Netherlands towns, Tijdschrift voor Economische en Sociale Geografie, 1955, Vol. 46, pp. 105–119.