Reference

	Astronomical Constants from NASA : Astronomical/space constants and equations. - www.ksc.nasa.gov/facts/faq04.html
	EquationSheet.com : Searchable directory, arranged by field, of equations, constants, symbols and SI units. Also features LaTEX utilities, software links. - www.equationsheet.com/
	Physics and Science Reference by PhysLINK.com : Includes physical constants, online unit conversions, periodic table of elements, exact time, fundamental physical formulae and equations. - www.physlink.com/reference/Index.cfm
	RefScout : A weekly, scientific reference mailing service. Screens databases covering life and medical sciences for the key words or the combination of key words specified and will automatically update with any abstract that has come up during the last seven days. Free service. - www.refscout.com/
	The Constants and Equations Pages : Expanding reference resource for science, math and astronomy - www.tcaep.co.uk/

Standards