[1] [CITE[Document Structure – SVG 1.1 (Second Edition)]]
( ([TIME[2011-08-10 12:35:27 +09:00]] 版))
<http://www.w3.org/TR/2011/REC-SVG11-20110816/struct.html#UseElement>

[2] [CITE[IRC logs: freenode / #whatwg / 20140106]]
( ([TIME[2014-01-07 23:19:33 +09:00]] 版))
<http://krijnhoetmer.nl/irc-logs/whatwg/20140106#l-558>