Planar versus non-planar NN annihilation into mesons in the light of qq operators and the 1/N{sub c} expansion

It is argued that in the antiproton-proton annihilation into two mesons, pp{yields}m{sub 1}m{sub 2}, the origin of different restrictive angular momentum selection rules commonly obtained for planar annihilation diagrams A2 and for non-planar rearrangement diagrams R2 lies in the omission of momentum transfer between an annihilated antiquark-quark pair and a remaining quark or antiquark. If momentum transfer is included, there is no reason for dismissing one type of diagram in favor of another one. Some considerations in the large-N{sub c} limit of QCD equally shed light on the planar and non-planar contributions to the total NN{yields}m{sub 1}m{sub 2} annihilation amplitude.