 The triangular delta itself is sometimes confusingly called a "3-"j" symbol" (without the "m") in analogy to 6-"j" and 9-"j" symbols, all of which are irreducible summations of 3-"jm" symbols where no variables remain.The 3-"jm" symbols give the integral of the products of three spherical harmonics
with formula_19, formula_20 and formula_21 integers.Similar relations exist for the spin-weighted spherical harmonics if formula_22