[1] XML Signature Syntax and Processing Version 1.1 ( (2013-04-16 23:47:22 +09:00 版)) <http://www.w3.org/TR/2013/REC-xmldsig-core1-20130411/#function-here>
[2] XML Signature Syntax and Processing Version 2.0 (2013-02-05 03:22:09 +09:00 版) <http://www.w3.org/2008/xmlsec/Drafts/xmldsig-core-20/#sec-XPath>