“…We verified these by comparing computer-simulated and experimentally obtained topographs using a six-beam case (Okitsu et al, , 2006(Okitsu et al, , 2011 and three-, four-, five-, six-, eight-and 12-beam cases (Okitsu et al, 2012). Hereafter, Okitsu et al (2006), Okitsu et al (2011) and Okitsu et al (2012) are denoted by O et al 2006O et al , O et al 2011O et al and OIY 2012 In OIY 2012, the n-beam T-T equation was derived from the n-beam Ewald-Laue (E-L) theory, and vice versa by their Fourier transformation, which explicitly revealed a simple relationship between them described by a Fourier transform. Ishiwata et al (2010) reported X-ray rocking curves that were obtained by fast Fourier transformation of the X-ray amplitude in a three-beam topograph, and compared them with those computed by solving the eigenvalue problem of the three-beam E-L theory.…”