http://en.wikipedia.org/wiki/Atmospheric_pressure

http://kids.earth.nasa.gov/archive/air_pressure/index.html

http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/circulation/air_pressure_p_1.html

http://www.usatoday.com/weather/resources/askjack/wfaqpres.htm

http://www.wisegeek.com/what-is-air-pressure.htm

http://www.srh.noaa.gov/srh/jetstream/atmos/pressure.htm

http://kids.earth.nasa.gov/archive/air_pressure/weather.html

http://www.factmonster.com/ipka/A0769510.html

http://geography.about.com/od/climate/a/highlowpressure.htm

http://www.wxdude.com/page15.html