(and is therefore also real). The Clebsch–Gordan coefficients ⟨ j 1 m 1 j 2 m 2 | J M ⟩ can then be found from these recursion relations. The normalization is fixed by the requirement that the sum of the squares, which equivalent to the requirement that the norm of the state |[ j 1 j 2 ] J J ⟩ must be one.