Available at http://wps.prenhall.com/esm_rubenstein_humangeo_7/6/1647/421852.cw/index.html [Accessed 8 March 2012].
Available at http://wps.prenhall.com/esm_rubenstein_humangeo_7/6/1647/421852.cw/index.html [Accessed 8 March 2012].