Population Density Map WORLD
Source: http://www.nationsonline.org/maps/gppd-12in.jpg
Source: http://soils.usda.gov/use/worldsoils/mapindex/popden.html
http://www.fs.fed.us/wildflowers/rareplants/images/USA-2000-population-density_lg.gif
Source: http://student.britannica.com/eb/art/print?id=71476&articleTypeId=1
Ethiopia Population Density
Population Density Canada