1. BIPM (1999) Mutual recognition of national measurement standards and of calibration and measurement certificates issued by national metrology institutes. Bureau International des Poids et Mesures (BIPM), Pavillon de Breteuil, 92312 Sèvres Cedex, France. Internet: www.bipm.org
2. Haerri H (2001) metINFO 2:9–14, Internet:www.metas.ch
3. Dybkaer R, Örnemark U, Uldall A, Richter W (1999) Accred Qual Assur 4:349–351
4. Henrion A, Dube G, Richter W (1997) Fresenius J Anal Chem 358:506–508
5. Spitzer P, Eberhardt R, Schmidt I, Sudmeier U (1996) Fresenius J Anal Chem 356:178–181