Authors: R Feistel; R Wielgosz; S A Bell; M F Camões; J R Cooper; P Dexter; A G Dickson; P Fisicaro; A H Harvey; M Heinonen; O Hellmuth; H-J Kretzschmar; J W Lovell-Smith; T J McDougall; R Pawlowicz; P Ridout; S Seitz; P Spitzer; D Stoica; H Wolf Journal: Metrologia Date: 2015-12-15 Impact factor: 3.157