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本作品按照创作共用署名-相同方式共享 3.0 Unported许可证发布，完整的许可证
可以访问http://creativecommons.org/licenses/by-sa/3.0/deed.zh，或者发送
信件到Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305,
USA。许可证的摘要如下，之后是完整的法律文本，如果您希望使用其他许可证发布
本作品部分或全部内容，请联系作者Karl Fogel<kfogel@red-bean.com>。

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您可以自由： 

* 分享 – 复制、发行、展览、表演、放映、广播或通过信息网络传播本作品
* 重新修改 – 创作演绎作品

惟须遵守下列条件：

* 署名 – 您必须按照作者或者许可人指定的方式对作品进行署名。

* 相同方式共享 — 如果您改变、转换本作品或者以本作品为基础进行创作，
  您只能采用与本协议相同的许可协议发布基于本作品的演绎作品。 

* 对于本作品的任何复用或分发，必须清晰说明本作品的许可证条款，最佳
  的方法是提供本文的链接。

* 如果得到版权所有者的许可，以上所有条件可以免除。

* 本许可证未有任何内容损害或限制作者的道德权利。

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