[1] CSS Snapshot 2015 ( 版) <http://drafts.csswg.org/css-2015/>
[2] CSS Snapshot 2015 ( ( 版)) <http://www.w3.org/TR/2015/NOTE-css-2015-20151013/>
[3] Re: [css3-values][css3-speech] dB & calc() ( (Tab Atkins Jr.著, )) <https://lists.w3.org/Archives/Public/www-style/2016May/0096.html>
> On another topic (CSS Snapshot 2015), are SVG-related CSS properties considered out of CSS ?
> There are no mention of them in CSS2015.
They're maintained outside of the CSSWG (by the SVGWG), so we're not
currently including them in our Snapshots.