4Kids stay plugged in for longer, study finds[N].Washington Post, 2010-1-21.
5Ellen Edwards. Study Shows Ever More Kids Embrace a Plugged-In Lifestyle[N].Washington Post, 2005-3-10(C03).
6CNN. Are kids too plugged in? What's all that digital juggling doing to their brains, family life? [N]. Times, 2006-3-20 (0013 HKT). Posted: 1613 GMT.
7CDC. CDC Behavior Risk Factor Surveillance System Report [R]. 2006.
8National Wildlife Federation. Why Be Out There? [EB/OL] http://www.nwf.org/Be-Out-There/Why-Be-Out-There.aspx,2012.
