[1] Guide to the W3C XML Specification (XMLspec) DTD, Version 2.1, 2/24/2014, 11:47:01 PM, 8/24/2024, 2:45:20 AM https://www.w3.org/XML/1998/06/xmlspec-report.htm#AEN2757

[2] 関連: HTML の <element>, <attribute>