1. Davis K., World Urbanization 1950–1970, Volume 2: Analysis of Trends, Relationships and Developments, Population Monograph 9, Institute of International Studies, University of California, Berkeley, p. 20, 1972.
2. United Nations, Urbanization: Development Policies and Planning (ST/SOA/Ser.X/1), United Nations Organization, New York, pp. 44, 47, 1968.