Tofful, A; Baynham, C F A; Curtis, A; Parsons, A O; Robertson, B I; Schioppo, M; Tunesi, J; Margolis, H S; Hendricks, R J; Whale, J; Thompson, R C; Godum, R M (2024) 171Yb+ optical clock with 2.2 × 10−18 systematic uncertainty and absolute frequency measurements. Metrologia, 61 (4). 045001