1. Anon 1976 Simultaneous Determination of Phosphorus, Magnesium, Calcium and Potassium. Technicon Canada Ltd, Montreal, Canada, Industrial Method No 237–72A.
2. Anon 1979 Analytical Methods for Flame Spectroscopy. Varian Techtron Pty Ltd, Springvale, Australia.
3. Anon 1981 Determination of Kjeldahl nitrogen content with Kjeltec Autosystems I, II, III, and IV. Application Note 30181, Tecator A B, Höganäs, Sweden.
4. AOAC 1981 Official Methods of Analysis (14th edn). Association of Official Analytical Chemists, Washington, DC.
5. APHA 1979 Standard Methods for the Examination of Water and Wastewater (14th edn). American Public Health Association, Washington, DC.