  A review is given of a recently developed technique for the analysis of
SO(2N) invariant couplings which allows a full exhibition of the SU(N)
invariant content of couplings involving the SO(2N) semi-spinors $|\Psi_{\pm}>$
with chiralilty $\pm$ and tensor representations. We discuss the Basic Theorem
used in the analysis and then exhibit the technique by illustrative examples
for the computation of the trilinear and quartic couplings for the SO(10) case
involving three generations of 16 plets of matter.
