1. Thompson M, Wood R (1993) JAOAC Intl 76:926–940
2. ISO (1997) Proficiency testing by interlaboratory comparisons. Part 1. Development and operation of proficiency testing schemes. ISO Guide 43-1, ISO, Geneva
3. Lawn RE, Thompson M, Walker RF (1997) Proficiency testing in analytical chemistry. RSC, Cambridge, UK
4. ISO (1994) Quality systems model for quality assurance in design, development, production, installation and servicing. ISO 9001, ISO, Geneva
5. ISO (1999) General requirements for the competence of testing and calibration laboratories. ISO/IEC 17025, ISO, Geneva