  The agreement between string theory and field theory is demonstrated in the
leading order by providing the first calculation of the correlator of three
two-impurity BMN states with all non-zero momenta. The calculation is performed
in two completely independent ways: in field theory by using the large-$N$
perturbative expansion, up to the terms subleading in finite-size, and in
string theory by using the Dobashi-Yoneya 3-string vertex in the leading order
of the Penrose expansion. The two results come out to be completely identical.
