[1]

border-box
content-box

[2] CSS Basic User Interface Module Level 3 (CSS3 UI) ( (Tantek Çelik 著, 2012-01-13 20:03:30 +09:00 版)) http://www.w3.org/TR/2012/WD-css3-ui-20120117/#box-sizing

[3] User Interface Enhancements ( (1999-09-16 05:07:02 +09:00 版)) http://www.w3.org/TR/1999/WD-css3-userint-19990916#box-sizing

[4] Issue #9. Add alias for -webkit-box-sizing. · whatwg/compat@e0a9b6c (2015-11-19 16:27:18 +09:00 版) https://github.com/whatwg/compat/commit/e0a9b6c2f6759b70108081a47470ab51ee67c04e

[5]

+ JavaScript の質問用スレッド vol.62 + (2015-12-24 22:46:18 +09:00 版) http://pc11.2ch.net/test/read.cgi/hp/1198422525/703

document.defaultView.getComputedStyle(element, null).getPropertyValue('width');
標準モードでFirefox, Opera, Safariで確認したのですが、
Opera (v9.25) のみ、paddingとborderを含んだ値が返って来ます

[6] [css-sizing] Import full propdef tables for all sizing properties, an… (tabatkins著, 2017-12-05 09:40:50 +09:00) https://github.com/w3c/csswg-drafts/commit/aab263247a81dce2d2c4be5e6653d46ee63e261d

[7] [css-ui-4][css-sizing] Moving box-sizing to the right spec · Issue #1906 · w3c/csswg-drafts (2017-12-08 15:44:34 +09:00) https://github.com/w3c/csswg-drafts/issues/1906