¹ Centro Nacional de Metrologia (CENAM), CP 76900, Querétaro, Qro, Mexico
² National Physical Laboratory (NPL), Teddington, Middlesex, TW11 0LW, UK
³ Center for Measurement Standards, Industrial Technology Research Institute (CMS/ITRI), Hsinchu, Taiwan 300
⁴ Institute for National Measurement Standards, National Research Council (INMS/NRC), Ottawa, Ontario, K1A 0R6, Canada
⁵ Korea Research Institute of Standards and Science (KRISS), Box 102 Yousung, Taejon, 305-600, Korea
⁶ Bureau International des Poids et Mesures (BIPM), Pavillon de Breteuil, F-92310, Sèvres Cedex, France
⁷ National Metrology Laboratory (CSIR-NML), PO Box 395, Pretoria 0001, South Africa
⁸ Metrologie und akkreditierung schweiz (METAS), Lindenweg 50, CH-3003 Bern-Wabern, Switzerland
⁹ Swedish National Testing and Research Institute (SP), PO Box 857, SE-50115 Boräs, Sweden
¹⁰ Standards, Productivity and Innovation Board (SPRING Singapore), 1 Science Park Drive, Singapore 118221, Singapore
¹¹ Instituto Nacional de Metrologia (INMETRO), Av. N.S. das Graças, 50-Xerém, Duque de Caxias–RJ, Brazil 25250-020
¹² Laboratoire national de métrologie et d'essais (LNE), 1, Rue Gaston Boissier, 75015 Paris, France
¹³ Centro Español de Metrologia (CEM), c/ del Alfar, 2 – Apartado 37, 28760 Tres Cantos (Madrid), Spain
¹⁴ National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST), Central 3, 1-1, Umezono 1-chome, Tsukuba, 305-8563, Japan
¹⁵ Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
¹⁶ Measurement Standards Laboratory of New Zealand, Industrial Research Limited (MSL), PO Box 31310, Lower Hutt, New Zealand
¹⁷ Nederlands Meetinstituut, Van Swinden Laboratorium (NMi-VSL), Thijsseweg 11, Box 654, 2600 AR Delft, The Netherlands
¹⁸ Present address: European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, B-2440 Geel, Belgium.