  This paper studies the incompressible limit of global strong solutions to the
three-dimensional compressible Navier-Stokes equations associated with Navier's
slip boundary condition, provided that the time derivatives, up to first order,
of solutions are bounded initially. The main idea is to derive a differential
inequality with decay, so that the estimates are bounded uniformly both in the
Mach number 0<\epsilon<=\epsilon 0 for some \epsilon 0>0 and the time t>=0.
