1. F. J. Monkhouse and H. R. Wilkinson, Maps and Diagrams, second edition, Methuen, London (1964), pp. 254–6.
2. A useful introductory account which touches on many themes in this chapter is given by J. W. Alexander, International trade: selected types of world regions, Economic Geography, 36 (1960), pp. 95–115.
3. E. Thorbecke, European economic integration and the patterns of world trade, American Economic Association Papers, 53 (1963), pp. 147–74,
4. and M. Kaser, COMECON: integration problems of the planned economies, Oxford University Press, London (1967).
5. G. G. Weigend, Some elements in the study of port geography, Geographical Review, 48 (1958), pp. 185–200.