http://images.google.com/images?q=%E5%87%A4%E5%87%B0&svnum=10&hl=zh-CN&lr=&newwindow=1&start=0&sa=N
请参看此图http://gallery.inlishui.com/albums/userpics/8_bainiaochaofeng/656816-n1-embed.jpg
用百度查