  In a recent paper [1] we have constructed the spin and tensor representations
of SO(4) from which the invariant weight can be derived for the Barrett-Crane
model in quantum gravity. By analogy with the SO(4) group, we present the
complexified Clebsch-Gordan coefficients in order to construct the
Biedenharn-Dolginov function for the SO(3,1) group and the spherical function
as the Lorentz invariant weight of the model.

General Relativity and Quantum Cosmology