1. ISO Guide 30, Terms and Definitions used in connection with Referene Materials, ISO, Geneva, 1992.
2. Analytical Chemists Committee of ICI, Standardisation of volumetric solutions, Analyst, 577 (1950) 75.
3. Analytical Standards Sub-Committee of the RSC, Sodium carbonate as a primary standard in acid-base titrimetry, Analyst 251 (1965) 90.
4. ISO Guide 31, Contents of Certificates of Reference Materials, ISO, Geneva, 1981.
5. ISO Guide 34, Quality System Guidelines for the Production of Reference Materials, ISO, Geneva, 1996.