Fractional Multi-Trace Fields of N=4 SYM_4 from AdS/CFT
  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. 
Thorsten Leonhardt, Ahmed Meziane and Werner Ruehl