  Exploiting final-state interactions and/or identity interference, analysis of
anisotropic correlations of particles at low-relative velocities yields
information on the anisotropy of emission sources in heavy-ion reactions. We
show that the use of cartesian surface-spherical harmonics in such analysis
allows for a systematic expansion of the correlations in terms of real
angular-moment coefficients dependent on relative momentum. The coefficients
are directly related to the analogous coefficients for emission sources. We
illustrate the analysis with an example of correlations generated by classical
Coulomb interaction.
