http://www.tcreng.com/download/material-conversion-table.shtml
http://www.webcivil.com/readusShapeWT.aspx
http://www.themeter.net/conv9_e.htm
http://www.grantadesign.com/resources/materials/designations/ferrous.generalcastiron.htm
http://www.daimi.au.dk/~ace/smartStuff/foottometer.html
http://www.portlandbolt.com/steel-plate-weight.html
http://www.calculatorsoup.com/calculators/conversions/
http://www.worldsteelprices.com/
http://www.americanfastener.com/technical/grade_markings_steel.asp