[1] XML Signature Syntax and Processing Version 2.0 ( 版) <http://www.w3.org/2008/xmlsec/Drafts/xmldsig-core-20/#sec-ReferenceProcessingModel>
In this specification, a 'same-document' reference is defined as a URI-Reference that consists of a hash sign ('#') followed by a fragment or alternatively consists of an empty URI [URI].
[2] [css-values] Revert the 'url(#foo) in an external stylesheet refers t… ( (tabatkins著, )) <https://github.com/w3c/csswg-drafts/commit/cc473b6c8de6c7ac57ab7559faf8cd0c47f7826c>
[3] Make fragment-only URLs always same-document. Closes #61.' ( (nikosandronikos著, )) <https://github.com/w3c/svgwg/commit/f378b15b95841cb1297eda7b1a6a2ca2d549ee71>
[4] amphtml/amp-html-format.md at master · ampproject/amphtml () <https://github.com/ampproject/amphtml/blob/master/spec/amp-html-format.md>
"xlink:href": only URIs starting with "#" are allowed