[1] calc() - CSS | MDN ( (2017-05-08 08:52:43 +09:00)) https://developer.mozilla.org/en/docs/Web/CSS/calc

[2] [css3-values] dropping min()/max() on calc() ( (L. David Baron著, 2010-09-09 05:39:05 +09:00)) https://lists.w3.org/Archives/Public/www-style/2010Sep/0233.html

[3] [css-values] Allow division of same types in calc() · Issue #545 · w3c/csswg-drafts (2018-06-15 12:24:28 +09:00) https://github.com/w3c/csswg-drafts/issues/545