  We prove inductively that every k-trace operator of SO(6)_R irrep with Young
tableau partition {r_1,r_2,r_3}, constructed out of k chiral primaries in the
twenty dimensional SO(6)_R irrep, leads to a quasi primary field with protected
conformal dimension. Our argument is based on perturbative evaluations of
certain four point functions up to order 1/N^2.
