[1] Document Structure – SVG 1.1 (Second Edition) ( ( 版)) http://www.w3.org/TR/2011/REC-SVG11-20110816/struct.html#UseElement
[2] IRC logs: freenode / #whatwg / 20140106 ( ( 版)) http://krijnhoetmer.nl/irc-logs/whatwg/20140106#l-558
[3] Issue 313438 - chromium - Lets rip out the SVG instance tree - An open-source project to help move the web forward. - Google Project Hosting ( ( 版)) https://code.google.com/p/chromium/issues/detail?id=313438
[4] 508561 – SVGUseElement has no instanceRoot attribute (SVG DOM) ( ( 版)) https://bugzilla.mozilla.org/show_bug.cgi?id=508561
[5] Removing the SVG instance tree (SVG2 issue 51) ( (Philip Rogers 著, 版)) http://lists.w3.org/Archives/Public/www-svg/2014Jan/0014.html