and similarly for J. The three J matrices are each (2 m + 1)×(2 m + 1) square matrices, and the three J are each (2 n + 1)×(2 n + 1) square matrices. The integers or half-integers m and n numerate all the irreducible representations by, in equivalent notations used by authors: D ≡ (m, n) ≡ D ⊗ D, which are each [(2 m + 1)(2 n + 1)]×[(2 m + 1)(2 n + 1)] square matrices.