References
- Dent, B.D. (2008) Cartography – Thematic Map Design (6th ed.) New York: McGraw-Hill.
- Robinson, A.H., Morrison, J.L., Muehrcke, P. Kimerling, A.J. and Gubtill, S. (1995) Elements of Cartography (6th ed.) New York: John Wiley.
- Slocum, T.A., McMaster, R.B., Kessler, F.C. and Howard, HH. (2008) Thematic Cartography and Geovisulization (3rd ed.) Upper Saddle River, New Jersey: Pearson Prentice Hall.