1. Cf. Raymond E. Murphy: Central Business District Research,inKnut Norborg, Edit.: Proceedings of the IGU Symposium in Urban Geography, Lund, 1960 (Lund, Sweden, 1962), pp. 473–483.
2. Jean Gottmann: Megalopolis, The Urbanized Eastern Seaboard of the United States (New York, 1961).
3. Walter M. Whitehill: A Topographical History of Boston (Cambridge, 1959), p. 42.
4. Samuel E. Morison: The Maritime History of Massachusetts, 1783–1860 (Cambridge, 1961), pp. 160–212.