(A) Because of linearity, the potential at a point P in the volume conductor is linearly proportional to dipoles in each coordinate direction.

(B) By superposition the potential at the point P is proportional to the sum of component dipoles in each coordinate direction. This proportionality is three-dimensional and can therefore be considered as a vector , called lead vector.

(C) The potential at the point P is the scalar product of the source dipole and the lead vector .