>>3
http://www.alles.or.jp/~torutk/oojava/maneuver/2000/6-3.html#SEC2
http://oss.timedia.co.jp/index.fcgi/kahua-web/show/XP%a4%c7%b3%da%a4%b7%a4%a4%bf%cd%c0%b8%a4%f2/XP%ca%aa%b8%ec/%bc%ea%ba%ee%b6%c8%a4%ce%a5%c6%a5%b9%a5%c8