http://www.etymotic.com
http://www.innerfidelity.com/images/EtymoticER4PT.pdf
http://ifs.nog.cc/bbsitake.hp.infoseek.co.jp/er-4s_intro.htm
http://ifs.nog.cc/bbsitake.hp.infoseek.co.jp/er-4b_intro.htm
http://sonove.angry.jp/about_localization.html
http://fuchinove.ninja-mania.jp/temp2.html
http://fuchinove.ninja-mania.jp/canalsokuteikekka.html