Portsmouth Polytechnic. Cartographic Unit. (1987). World mapping today. Butterworths.
Cita Chicago (17th ed.)Portsmouth Polytechnic. Cartographic Unit. World Mapping Today. London: Butterworths, 1987.
Cita MLA (9th ed.)Portsmouth Polytechnic. Cartographic Unit. World Mapping Today. Butterworths, 1987.
Atenció: Aquestes cites poden no estar 100% correctes.