ELECTRONIC	h   t   t   p   c o l o n   s l a s h   s l a s h   h y p e r p h y s i c s dot p   h   y   d a s h   a   s   t   r dot g   s   u dot e   d   u   s l a s h	http://hyperphysics.phy-astr.gsu.edu/	1