[1] Touch.force - Web API interfaces | MDN ( (2013-09-30 13:00:31 +09:00 版)) <https://developer.mozilla.org/en-US/docs/Web/API/Touch.force>

[2] Touch Events Extensions ( (2013-10-29 05:03:47 +09:00 版)) <http://www.w3.org/TR/2013/NOTE-touch-events-extensions-20131031/#widl-Touch-force>