[1] Guide to the W3C XML Specification (XMLspec) DTD, Version 2.1, 2014-02-24T23:47:01.000Z, 2024-08-24T02:45:20.945Z https://www.w3.org/XML/1998/06/xmlspec-report.htm#AEN2757

[2] 関連: HTML の <element>, <attribute>