“…Laue, 1960) was very clear to authors of the pioneering papers (Zachariasen, 1967;Becker & Coppens, 1974, B&C hereinafter;Wemer, 1974). Later, there were several papers (Kato, 1976;Becker, 1977;Olekhnovich & Olekhnovich, 1978;Becker & Dunstetter, 1984;Werner et al, 1986;A1 Haddad & Becker, 1990, H&B hereinafter), in which the general approach to evaluate the primary-extinction factor by use of the dynamical Takagi-Taupin equations (Takagi, 1962(Takagi, , 1969Taupin, 1964Taupin, , 1967 was discussed. A meaningful primary-extinction solution (except for X-ray absorption) was first found by Kato (1976) and Becker (1977) and corresponds to the Laue approximation of the pointsource diffractive function that describes X-ray diffraction by finite convex-shaped crystals.…”