Sr Lattice Clock at 1 × 10 <sup>–16</sup> Fractional Uncertainty by Remote Optical Evaluation with a Ca ClockAndrew D. Ludlow, C. W. Oates, Michael J. Martin et al.|Science|2008Cited by 549
Frequency ratio measurements at 18-digit accuracy using an optical clock networkK. Beloy, X. Zhang, A. Sophia Koepke et al.|Nature|2021Cited by 367