This is simply done by applying the d'Alembert operator ◻ ◻ = ( ∇ ∇ 2 − − 1 c 2 ∂ ∂ 2 ∂ ∂ t 2 ) to both vectors, keeping in mind that c 2 = ( μ μ ϵ ϵ ) − − 1 , and the result is non-zero due to the polarizations that are present. This provides a direct pathway between easily determined properties such as current density J to fields via the Hertz vectors and their relations to the scalar and vector potentials. These wave equations yield the following solutions for the Hertz vectors: