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3. C.W. Bunn, Chemical Crystallography, 2nd ed., p. 192, Oxford University Press, London (1961).
4. R.W. James, Optical Principles of the Diffraction of X-Rays, p. 606, Bell & Sons, London (1964).
5. International Tables for X-Ray Crystallography, Vol. III. p. 295. Kynoch Press. Birmingham (1962).