[1] Web Forms 2.0 (2009-01-05 20:07:15 +09:00 版) <http://www.whatwg.org/specs/web-forms/current-work/#stepup>

[2] [whatwg] More stepUp() and stepDown() comments (was: Re: Forms-related feedback) ( (2013-01-30 19:43:58 +09:00 版)) <http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2013-January/038826.html>