[
  {
    "id": "ef-21-1",
    "type": "article-journal",
    "title": "Systematic evaluation of an atomic clock at 2 × 10−18 total uncertainty",
    "author": [
      {
        "given": "T.L.",
        "family": "Nicholson"
      },
      {
        "given": "S.L.",
        "family": "Campbell"
      },
      {
        "given": "R.B.",
        "family": "Hutson"
      },
      {
        "given": "G.E.",
        "family": "Marti"
      },
      {
        "given": "B.J.",
        "family": "Bloom"
      },
      {
        "given": "R.L.",
        "family": "McNally"
      },
      {
        "given": "W.",
        "family": "Zhang"
      },
      {
        "given": "M.D.",
        "family": "Barrett"
      },
      {
        "given": "M.S.",
        "family": "Safronova"
      },
      {
        "given": "G.F.",
        "family": "Strouse"
      },
      {
        "given": "W.L.",
        "family": "Tew"
      },
      {
        "given": "J.",
        "family": "Ye"
      }
    ],
    "container-title": "Nature Communications",
    "issued": {
      "date-parts": [
        [
          2015
        ]
      ]
    },
    "DOI": "10.1038/ncomms7896",
    "URL": "https://doi.org/10.1038/ncomms7896"
  },
  {
    "id": "ef-21-2",
    "type": "article-journal",
    "title": "Resolving the gravitational redshift across a millimetre-scale atomic sample",
    "author": [
      {
        "given": "Tobias",
        "family": "Bothwell"
      },
      {
        "given": "Colin J.",
        "family": "Kennedy"
      },
      {
        "given": "Alexander",
        "family": "Aeppli"
      },
      {
        "given": "Dhruv",
        "family": "Kedar"
      },
      {
        "given": "John M.",
        "family": "Robinson"
      },
      {
        "given": "Eric",
        "family": "Oelker"
      },
      {
        "given": "Alexander",
        "family": "Staron"
      },
      {
        "given": "Jun",
        "family": "Ye"
      }
    ],
    "container-title": "Nature",
    "issued": {
      "date-parts": [
        [
          2022
        ]
      ]
    },
    "DOI": "10.1038/s41586-021-04349-7",
    "URL": "https://doi.org/10.1038/s41586-021-04349-7"
  },
  {
    "id": "ef-21-3",
    "type": "article-journal",
    "title": "Frequency ratio measurements at 18-digit accuracy using an optical clock network",
    "author": [
      {
        "given": "",
        "family": "Boulder Atomic Clock Optical Network (BACON) Collaboration*"
      },
      {
        "given": "Kyle",
        "family": "Beloy"
      },
      {
        "given": "Martha I.",
        "family": "Bodine"
      },
      {
        "given": "Tobias",
        "family": "Bothwell"
      },
      {
        "given": "Samuel M.",
        "family": "Brewer"
      },
      {
        "given": "Sarah L.",
        "family": "Bromley"
      },
      {
        "given": "Jwo-Sy",
        "family": "Chen"
      },
      {
        "given": "Jean-Daniel",
        "family": "Deschênes"
      },
      {
        "given": "Scott A.",
        "family": "Diddams"
      },
      {
        "given": "Robert J.",
        "family": "Fasano"
      },
      {
        "given": "Tara M.",
        "family": "Fortier"
      },
      {
        "given": "Youssef S.",
        "family": "Hassan"
      },
      {
        "given": "David B.",
        "family": "Hume"
      },
      {
        "given": "Dhruv",
        "family": "Kedar"
      },
      {
        "given": "Colin J.",
        "family": "Kennedy"
      },
      {
        "given": "Isaac",
        "family": "Khader"
      },
      {
        "given": "Amanda",
        "family": "Koepke"
      },
      {
        "given": "David R.",
        "family": "Leibrandt"
      },
      {
        "given": "Holly",
        "family": "Leopardi"
      },
      {
        "given": "Andrew D.",
        "family": "Ludlow"
      },
      {
        "given": "William F.",
        "family": "McGrew"
      },
      {
        "given": "William R.",
        "family": "Milner"
      },
      {
        "given": "Nathan R.",
        "family": "Newbury"
      },
      {
        "given": "Daniele",
        "family": "Nicolodi"
      },
      {
        "given": "Eric",
        "family": "Oelker"
      },
      {
        "given": "Thomas E.",
        "family": "Parker"
      },
      {
        "given": "John M.",
        "family": "Robinson"
      },
      {
        "given": "Stefania",
        "family": "Romisch"
      },
      {
        "given": "Stefan A.",
        "family": "Schäffer"
      },
      {
        "given": "Jeffrey A.",
        "family": "Sherman"
      },
      {
        "given": "Laura C.",
        "family": "Sinclair"
      },
      {
        "given": "Lindsay",
        "family": "Sonderhouse"
      },
      {
        "given": "William C.",
        "family": "Swann"
      },
      {
        "given": "Jian",
        "family": "Yao"
      },
      {
        "given": "Jun",
        "family": "Ye"
      },
      {
        "given": "Xiaogang",
        "family": "Zhang"
      }
    ],
    "container-title": "Nature",
    "issued": {
      "date-parts": [
        [
          2021
        ]
      ]
    },
    "DOI": "10.1038/s41586-021-03253-4",
    "URL": "https://doi.org/10.1038/s41586-021-03253-4"
  }
]