  An approximately globally convergent numerical method for a 3d Coefficient
Inverse Problem for a hyperbolic equation with backscattering data is
presented. A new approximate mathematical model is presented. An approximation
is used only on the first iteration and amounts to the truncation of a certain
asymptotic series. A significantly new element of the convergence analysis is
that the so-called "tail functions" are estimated. Numerical results in 2d and
3d cases are presented, including the one for a quite heterogeneous medium.
