[3] ASCII英数字 >>1 (alphanumeric SACII characters >>5) は、 ASCII英字とASCII数字です。
[4] ASCII十六進数字はすべてASCII英数字です。
[7] Refactor tag states and actions (#994) · whatwg/html@b66ec32 ( 版) https://github.com/whatwg/html/commit/b66ec320db01c12d48176052c3b9cd55a10f3176
[8] Editorial: start using the Infra Standard (annevk著, ) https://github.com/whatwg/url/commit/9001b9be7475fdf4a7a2757b5417aa4a9f06b3b6
[9] Editorial: use more terms from the Infra Standard (annevk著, ) https://github.com/whatwg/html/commit/104bd78697738af2eab61740a2f1421ae49a3c95
[10] rfc4151, https://datatracker.ietf.org/doc/html/rfc4151#section-2.1