%0 Journal Article %A Sébastien Bize %T The unit of time: Present and future directions %J Comptes Rendus. Physique %D 2019 %P 153-168 %V 20 %N 1-2 %I Elsevier %R 10.1016/j.crhy.2019.02.002 %G en %F CRPHYS_2019__20_1-2_153_0