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3. Reynoldson, T. B., Proc. Inst. Sew. Purif., 1941 (in the press).
4. "Methods of Chemical Analysis as applied to Sewage and Sewage Effluents" (H.M. Stationery Office, 1929).
5. Chambers, E. G., "Statistical Calculation for Beginners" (Cambridge Univ. Press, 1940).