by the optical theorem, is equal to the $\gamma^*$-A total cross section or, equivalently, $\nu W_2.$ The first term on the right-hand side of Fig.10 represents the incoherent scattering off the A nucleons in the nucleus, the nucleons being labeled by $N_i.$ The second term on the right-hand side of the figure represents the double scattering term which is dominated by diffractive scattering, off nucleon $N_i$ in the amplitude and $N_j$ in the complex conjugate amplitude. So long as shadowing correction are not too large it should not be necessary to go beyond the double scattering term. Indeed, the double scattering term can be obtained from diffractive data at HERA while triple and higher scattering terms would involve the scattering of partonic systems in the nucleus, terms which cannot be reliably determined. Using a parametrization which fits the HERA diffractive data, a pretty good description of fixed target deep inelastic scattering of nuclei is obtained with the double scattering term giving a shadowing correction of about the right size\[15\].

$J/\psi$ production in proton-nucleus and nucleus-nucleus collisions
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Recently there has been much interest, and excitement, about the NA50 data\[18\]. In a nutshell one can summarize the experimental situation as follows: 