[1] 天文時計 - Wikipedia (2017-07-04 23:32:28 +09:00) <https://ja.wikipedia.org/wiki/%E5%A4%A9%E6%96%87%E6%99%82%E8%A8%88>

[2] Astronomical clock - Wikipedia (2018-06-27 13:13:41 +09:00) <https://en.wikipedia.org/wiki/Astronomical_clock>