ALEXANDER, J. W., & GIBSON, L. J. (1979). Economic geography.-- ed.2. Prentice Hall.

ALEXANDER, John W., and Lay James GIBSON. Economic Geography.-- Ed.2. London: Prentice Hall, 1979.

ALEXANDER, John W., and Lay James GIBSON. Economic Geography.-- Ed.2. Prentice Hall, 1979.