Comments on "Comparative Analysis of Acceleration Techniques for 2-D and 3-D Green\´s Functions in Periodic Structures Along One and Two Directions"

The paper by Valerio et al. (2007), contains a lot of useful information on the problem of efficient calculation of the periodic Green´s function. However, making their review of the existing methods, the authors have missed one approach, which, in our opinion, deserves attention as well. That approach was originally proposed by Ivanishin (2002) for calculating the Green´s function of a rectangular waveguide. Later, it was generalized and successfully applied in (Skobelev and Mukhamedov, 1993) and (Skobelev, 2002) for solving 2D and 3D problems associated with analysis of 1D- and 2D-periodic arrays, respectively.