[1] Greenwich Time: And the Discovery of the Longitude - Derek Howse - Google ブックス () <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 () <https://archive.org/details/GreenwichTime>