[1] DOM 4 request ( (Richard Schwerdtfeger 著, 2013-03-10 06:05:10 +09:00 版)) http://lists.w3.org/Archives/Public/www-dom/2013JanMar/0171.html

[2] [whatwg] Document.activeElement should return the root element in non-HTML documents when no element has focus ( (2014-02-03 19:43:13 +09:00 版)) http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2014-February/041974.html

[3] Editorial: synchronize with the DOM Standard · whatwg/html@21c6ec7 (2016-03-20 18:16:07 +09:00 版) https://github.com/whatwg/html/commit/21c6ec77594eb89b836d4872222f5916910967fd

[4] Editorial: cleanup activeElement (annevk著, 2018-03-05 10:33:24 +09:00) https://github.com/whatwg/html/commit/4823cf596e2ce499f3be67b486ffea261cbe4b29

[5] Editorial: cleanup activeElement by annevk · Pull Request #3513 · whatwg/html (2018-03-06 17:39:12 +09:00) https://github.com/whatwg/html/pull/3513

[6] Define DocumentOrShadowRoot's activeElement (rakina著, 2019-08-24 03:26:07 +09:00) https://github.com/whatwg/html/commit/5b84d194c5ca0be9b738e0d46078131ca4a5f422

[7] Define DocumentOrShadowRoot.activeElement by rakina · Pull Request #4837 · whatwg/html (2020-01-12 16:54:32 +09:00) https://github.com/whatwg/html/pull/4837

[8] Shadow DOM and focus · Issue #1583 · whatwg/html (2020-01-12 16:54:58 +09:00) https://github.com/whatwg/html/issues/1583