[1] Greenwich Time: And the Discovery of the Longitude - Derek Howse - Google ブックス (2017-06-20 19:22:30 +09:00) https://books.google.co.jp/books/about/Greenwich_Time.html?id=YOzaAAAAMAAJ&redir_esc=y

[2] Greenwich Time : Derek Howse : Free Download & Streaming : Internet Archive (2017-06-20 19:23:49 +09:00) https://archive.org/details/GreenwichTime