  Complexified spacetime algebra is defined as the geometric (Clifford) algebra
of spacetime with complex coefficients, isomorphic $\mathcal{G}_{1,4}$. By
resorting to matrix representation by means of Dirac-Pauli gamma matrices, the
paper demonstrates isomorphism between subgroups of CSTA and SU(3). It is shown
that the symmetry group of those subgroups is indeed $U(1) \otimes SU(2)
\otimes SU(3)$ and that there are 4 distinct copies of this group within CSTA.
