[1] HTTP Status Codes (Dan McCormick 著, 版) http://www.mccormickfamily.com/become-an-author/56-http-status-codes#509
[2] List of HTTP status codes - Wikipedia, the free encyclopedia ( ( 版)) http://en.wikipedia.org/wiki/List_of_HTTP_status_codes
[3] List of HTTP status codes - Wikipedia, the free encyclopedia ( ( 版)) http://en.wikipedia.org/wiki/List_of_HTTP_status_codes#509
509 - Returned if the bandwidth limit for the user or repository has been exceeded. The API does not specify any bandwidth limit, but implementors may track usage.
[5] 509 Bandwidth Limit Exceeded, , https://web.archive.org/web/20260530064208/https://www.bibliaimpex.com/books/pdfs/9783945151044.pdf