2. One of the outstanding prerequisites of any city is a local transportation system which makes possible ready access of the population living in diverse sections to their places of work, the centers of trade, of culture, and of other social activities. The city consists of not merely a continuous densely populated and built up area, but of suburbs and outlying regions which by means of rapid transit are within easy reach of urban activities. This area has been termed the commuting area. Although the inhabitants of this larger area of settlement may not be under the same taxing, policing, and governing authorities as the inhabitants of the city proper, they think of themselves as part of the same metropolis and actively participate in its life. Edel, Edmund. _Neu Berlin_, volume L in “Grossstadt Dokumente Series,” edited by Hans Ostwald, Berlin, 1905. Discusses the changes brought about by recent growth in the city of Berlin, with emphasis on the recently built-up suburbs. (VII, 1, 2, 4.) Lueken, E. “Vorstadtprobleme,” _Schmollers Jahrb._, XXXIX (1915), 1911–20. Discussion of the governmental and technical problems brought about by the rise of the suburbs. (IV, 3; V, 1; VI.) Wright, Henry C. “Rapid Transit in Relation to the Housing Problem,” in _Proceedings of the Second National Conference on City Planning_ (Rochester, 1910), pp. 125–35. Considers the possibility of distributing the urban population in the suburbs by building up a rapid transit system. (VI, 2, 3, 10.) 3. That part of the inhabitants of a given metropolitan area who actually are under the same administrative machinery may constitute only a relatively small part of the inhabitants of the metropolitan district as a whole. The size of the administrative unit tends to lag behind the size of the metropolis proper. Suburbs are incorporated gradually, and changes in charters and legal organization often do not keep pace with the rapid expansion of the district. The city of London proper is only a relatively small part of metropolitan London. As a result of such anomalous situations many difficulties occur in interpreting statistical data compiled by governmental agencies. Gross, Charles. _Bibliography of British Municipal History_ (New York, 1897). (I, 2; VI, 7.) Howe, Frederic C. _European Cities at Work_ (New York, 1913). A general survey of the structure and the government of the European city. (II, 3; VI; VII, 1.) ——. _The British City: The Beginnings of Democracy_ (New York, 1907). (II, 2, 3; VI.) Kales, Albert M. _Unpopular Government in the United States_ (Chicago, 1914). A discussion of the administrative problems of the city, emphasizing the anomalous situations brought about by legal restrictions in the face of urban development. (VI, 7; X, 1, 2.)