Chapter 23
www.census.gov/ipc/www/idb/
www.prb.org/
www.techkiva.com/teachcensus/PopPyr.htm
math.bu.edu/DYSYS/applets/
staff.science.uva.nl/~alejan/dynamicstour.html
www.census.gov/ipc/www/idb
http://forio.com/simulate/simulation/pontifexconsult/how-much-oil-is-left/