https://www.i-garden.org/blog/2009/12/16/google-wave%e5%9c%a8%e6%95%99%e5%ad%b8%e4%b8%8a%e7%9a%84%e6%87%89%e7%94%a8%e5%88%9d%e6%8e%a2-8-%e5%85%a5%e9%96%80%e6%8a%80%e5%b7%a7%e7%af%87/