https://doujinblog.org/%e5%90%8c%e4%ba%ba%e3%82%bd%e3%83%95%e3%83%88-130429-define-%e5%af%be%e7%95%b0%e5%bd%a2%e7%94%9f%e8%b4%84%e7%a5%9e%e5%ae%98%e3%83%86%e3%82%a3%e3%82%a2%e3%83%8a/