Two particle azimuthal angular correlations are one of the most sensitive and direct probes of gluon saturation in both proton-nucleus (pA) and electron nucleus (eA) collisions. In this talk we report on first results on the azimuthal angular correlation of three particles in the presence of saturation effects and on-going efforts in the determination of next-to-leading order corrections to dihadron correlations within the CGC-framework. While our calculation concentrates at first on the DIS case i.e. (virtual) photon - nucleus collisions predominantly studied in eA collisions, it also provides the necessary framework for the analogous (but more complex) calculations needed for the corresponding observable in pA collisions. Moreover, a direct study of the (virtual) photon - nucleus process seems to be possible in ultra-peripheral AA and pA collisions.