References

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Bureau of the Census, 2002. Historical Estimates of World Population. Retrieved 16 Aug 2002 from http://www.census.gov/ipc/www/worldhis.html.

Nemiroff, R. and J. Bonnell, 2001. A solar Prominence Erupts. Retrieved 6 Oct 2001 from http://antwrp.gsfc.nasa.gov/apod/ap010924.html.

Nemiroff, R. and J. Bonnell, 2001. M74: The Perfect Spiral. Retrieved 6 Oct 2001 from http://antwrp.gsfc.nasa.gov/apod/ap011004.html.

University Corporation for Atmospheric Research, 1995. Earth Photo by the Apollo 17 Crew. Retrieved 6 Oct 2001 from http://www.windows.ucar.edu/cgi-bin/tour_def/earth/images/earthafr_image.html.