“…The analytical formulation of this radiation problem is concise and somewhat Setting d 1 = 0 into (7), we arrive at the following formula [24]: By substitution into the right-hand side of (6), we obtain, because of (36), in this marginal case: δ se F (ι) α,mn,e (k 2 r 1 ) + δ so F (ι) α,mn,o (k 2 r 1 ) = F (ι) α,mn,s (k 2 r 1 ) , which is the left-hand side of (6). Hence, W α,mn,s α ′ ,m ′ n ′ ,s ′ ≡ δ αα ′ δ mm ′ δ nn ′ δ ss ′ , if d 1 = 0.…”