1. Anderson, J. S., Surface and Defect Properties of Solids (edit. by Roberts, M. W., and Thomas, J. M.), 1 (Chem. Soc. Specialist period. Rep., 1972).
2. Clapp, P. C., The Chemistry of Extended Defects in Non-Metallic Solids (edit. by Eyring, L., and O'Keefe, M.), 663 (North Holland, Amsterdam, 1970).
3. Tilley, R. J. D., MTP Reviews of Science (edit. by Roberts, L. E. J.), 10 (Butterworth, London, 1972).
4. Allpress, J. G., Sanders, J. V., and Wadsley, A. D., Acta cryst- allogr., B, 25, 1156 (1969).
5. Allpress, J. G., and Wadsley, A. D., J. Solid State Chem., 1, 28 (1969).