Combination of two spherical tensors A q 1 ( k 1 ) and B q 2 ( k 2 ) in the following manner involving the Clebsch–Gordan coefficients can be proved to give another spherical tensor of the form: T q ( k ) = ∑ ∑ q 1 , q 2 ⟨ ⟨ k 1 , k 2 ; q 1 , q 2 | k 1 , k 2 ; k , q ⟩ ⟩ A q 1 ( k 1 ) B q 2 ( k 2 )