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• The procedure of the method itself e.g. low values are inaccurate due to inevitable small errors in the measured time to collect the first filtered 500mL, e.g. due to pressure variations or inaccurate time reading. Proposed remedial action: No suggestions. • The principal weakness is that the flux decline is not measured after a fixed and certain flux decline has been observed or a certain and fixed volume has been filtered. Proposed remedial action: Determine the rate of flux decline over a period in which 75% plugging has taken place or measure the flux decline after a fixed volume has been filtered e.g. 15 L. • The large effect of the membrane resistance of the membrane on the result of the test—the higher the resistance the lower the measured value. Proposed remedial action: Narrow the range of allowable resistance of membrane filters used or apply correction factor as proposed by Alhadidi. • The absence of a correction for temperature—the higher the temperature the higher the measured value. Proposed remedial action: Measure SDI always at 25 C or apply correction factor as proposed by Alhadidi. • The observed variations in pore size and pore size distribution in the used membrane filters. Proposed remedial action: Identify/select/develop a type (brand) membrane with constant pore size and narrow pore size distribution. Develop simple method to verify these membrane properties.

A unified system for bibliographical references is described. The suggestions, which are in the main compatible with ISO DIS 690, allow the name/date (Harvard), the numeric-alphabetic or the sequential-numeric system to be used for references in scientific books and serials; an optional dual-access system is also outlined. The ‘master typescript’ system described allows numbers to be substituted for names/dates in the text when a paper is submitted to a publication that uses a numeric system. In reference lists, depending on what the author’s target publication requires, references must be arranged either alphabetically or sequentially, in the order of their citation in the text. In all lists, whether alphabetic or sequential, references should contain the same elements, arranged in the same order, as follows: Abel B C, Cain A D, Adam E, Eve A 1976 Bark thickness in apple trees. Tree J 12:90–99