A note on four-point functions of conformal operators in N=4 Super-Yang   Mills
  We find that the first-order correction to the free-field result for the four-point function of the conformal operator $\tr(\phi^i\phi^j)$ is nonvanishing and survives in the limit $N_c \rar \infty$. 
Francisco Gonzalez-Rey, Inyong Park, Koenraad Schalm