[1] 天文時計 - Wikipedia (7/4/2017, 2:32:28 PM) <https://ja.wikipedia.org/wiki/%E5%A4%A9%E6%96%87%E6%99%82%E8%A8%88>
[2] Astronomical clock - Wikipedia (6/27/2018, 4:13:41 AM) <https://en.wikipedia.org/wiki/Astronomical_clock>
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