1. ISO/IEC Guide 43 (1984, revised 1987) Proficiency testing by interlaboratory comparisons. ISO CASCO; ISO/IEC, Geneva
2. Thompson M, Wood R (1993) The international harmonised protocol for the proficiency testing of (chemical) analytical laboratories. Pure Appl Chem 65:2123–2144
3. ASTM E1301 (1995) Standard guide for proficiency testing by interlaboratory comparison. ASTM, Philadelphia
4. ISO 13528 (2005) Statistical methods for proficiency testing by interlaboratory comparisons. ISO TC/69. ISO, Geneva
5. ILAC G13 (2000, revised 2007) ILAC guidelines for the requirements for the competence of providers of proficiency testing schemes. ILAC, Sydney