1. DropTalk, http://droplet.ddo.jp/droptalk/.
2. Voice4u, http://voice4uaac.com/jp/.
3. TapToTalk, http://www.taptotalk.com/index.aspx .
4. Effects and limitations of communication aids. Journal of communication aids for people with cognitive disabilities;Nakamura;Higher brain function research,2001
5. VOCA application to Autistic Children;Sakai;National Welfare Foundation for Disabled Children,1999