From J.J. Zakurai page no.222-225:
We know that Clebsch-Gordan coefficients vanish unless m=m1+m2. Then,
(1) why is that the terms in recursion relation doesn't vanish? since m1+m2=m+1 or m1+m2=m-1 in eqn.(3.7.49).
(2) why is again in the example shown in eqn.(3.7.54), m1+m2=m?
I...