文章链接:http://mp.weixin.qq.com/s?__biz=MzIxMjAzNDY5Mg==&mid=2650791037&idx=1&sn=32abd47df6e6b47553cb472840649e9a&chksm=8f474996b830c08093c99120b438ff18e94674d34926aaa592f6778ec2923df84222365f991f&scene=21#wechat_redirect 原文: https://hit-scir.gitbooks.io/neural-networks-and-deep-learning-zh_cn/content/appendix.html