On the coupling between multiple scattering and absorption

In a recent paper [Acta Cryst. (1982), A38, 248-252], Borie discusses extinction in absorbing materials. He argues that the problem has been improperly analysed by Becker & Coppens. It is shown here that Borie's argument is wrong: Becker & Coppens solution is correct as far as absorption-extinction coupling is concerned, for crystals of general shape.