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2. Perrin, R. M. S., Clay Minerals Bull., 3, 193 (1957).
3. Kellaway, G. A., and Welch, F. B. A., The Bristol and Gloucester Districts, second ed. (Geol. Surv. Reg. Guides, HMSO, 1961).
4. American Petroleum Institute, Project 49, Clay Minerals Standards, prelim. reps, 1–8 (1963).
5. Dines, H. G., and Edmunds, F. H., The Country around Reigate and Dorking (Mem. Geol. Surv., GB, 1933).