[1] [CITE@en[Syntax and basic data types]]
( ([TIME[2011-04-16 03:28:12 +09:00]] 版))
<http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords>

[2] [CITE@en[Cascading Style Sheets (CSS) Snapshot 2007]]
( ([TIME[2011-05-12 23:25:26 +09:00]] 版))
<http://www.w3.org/TR/2011/NOTE-css-beijing-20110512/#experimental>

[3] [CITE@en[Cascading Style Sheets (CSS) Snapshot 2010]]
( ([TIME[2011-05-12 23:24:12 +09:00]] 版))
<http://www.w3.org/TR/2011/NOTE-css-2010-20110512/#experimental>