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3. D. P. Morris and J. L. Hughes, 1964. Acta Cryst., 17, 209–211.
4. J. J. Comer, 1964. Ibid., 17, 444–445.
5. E. Gillam, H. P. Rooksby and L. D. Brownlee, 1964. Ibid., 17, 762–763.