1. International Laboratory Accreditation Cooperation (ILAC): 2000, ILAC-G12: guidelines for the requirements for the competence of reference material producers, pp. 1–30. ILAC, Rhodes, Australia.
2. International Laboratory Accreditation Cooperation (ILAC): 2000, ILAC-G13: guidelines for the requirements for the competence of providers of proficiency testing schemes, pp. 1–23. ILAC, Rhodes, Australia.
3. International Organization for Standardization (ISO): 1989, ISO Guide 35: certification of reference materials—general and statistical principles, pp. 1–35. ISO, Geneva, Switzerland.
4. International Organization for Standardization (ISO): 1992, ISO Guide 30: terms and definitions used in connection with reference materials, pp. 1–13. ISO, Geneva, Switzerland.
5. International Organization for Standardization (ISO): 1997, ISO Guide 32: calibration in analytical chemistry and use of certified reference materials, pp. 1–8. ISO, Geneva, Switzerland.