The definitions above are according to the International System of Quantities (ISQ) upon which the SI is based. However, many tables of magnetic susceptibility give the values of the corresponding quantities of the CGS system (more specifically CGS-EMU, short for electromagnetic units, or Gaussian-CGS ; both are the same in this context). The quantities characterizing the permeability of free space for each system have different defining equations: B CGS = H CGS + 4 π π M CGS = ( 1 + 4 π π χ χ v CGS ) H CGS .