1. Huber PJ (1981) Robust statistics. Wiley, New York
2. International laboratory accreditation cooperation (2007) G13 - ILAC Guidelines for the requirements for the competence of providers of proficiency testing schemes, available from
http://www.ilac.org
3. ISO 13528:2005 - Statistical methods for use in proficiency testing by interlaboratory comparison
4. ISO/IEC 17043:2010 - Conformity assessment - General requirements for proficiency testing
5. ISO/TS 20612:2007 - Water quality - Interlaboratory comparisons for proficiency testing of analytical chemistry laboratories