http://penrosesteel.com/

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

http://www.factorysteel.com/steel-angles-bars-channels-i-beams.htm

http://www.efunda.com/math/areas/RolledSteelBeamsW.cfm

http://www.ibeams.com/

http://www.ibeams.co.za/index.htm

http://www.alibaba.com/catalogs/92504/Steel_I_Beams.html

http://www.steelliq.com/

http://www.howstuffworks.com/iron.htm

http://www.factorysteel.com/

http://rongyusteel.en.alibaba.com/product/254044357-209452234/I_beams_steel_JIS_.html

http://www.noblemetalsonline.com/steel.htm

http://www.wisegeek.com/what-is-a-steel-i-beam.htm

http://www.alibaba.com/product-gs/209878646/I_Beams_Steel.html

http://www.efunda.com/math/areas/IBeamIndex.cfm