  A method for the fast and accurate solution of the radiative transfer
equation in plane-parallel media with coherent isotropic scattering is
presented. This largely analytical approach uses the formalism of meromorphic
functions in order to obtain the total solution, i.e. the angle and depth
variation of the radiation field. A discretization of space and angle
coordinates is not required. For the further application in the accretion disks
a particular case of a finite slab whose the midplane is the symmetry plane is
considered.
