We assume the volume V with field is spherical with radius a. First we calculate the "transverse" part

where k ₀ = ?/ c, R( r)and Y( ?, ?) are the radial and angular parts of the Debye potential accordingly. In (A.1) through integrating by parts we calculate the radial integral as the following

where . The "longitude" part of electric energy has the following form

So the full electric part of energy becomes

The magnetic part of energy one can be calculated by a similar way

where (see Appendix B). We perform a change variable k ₀ r = y ₀, k ₀ dr = dy ₀ in the integral ? ^a ₀ R ² dr. Now and are given by

where ? = k ₀ a = ? a/c. Remember that R( y ₀) satisfies the equation

Equations for the TE fields can be derived by the similar way.