http://skyhigh233.com/blog/2017/04/01/ica-math/
https://danieljyc.github.io/2014/06/13/%E6%9C%BA%E5%99%A8%E5%AD%A6%E4%B9%A015-3--%E7%8B%AC%E7%AB%8B%E6%88%90%E5%88%86%E5%88%86%E6%9E%90ica%EF%BC%88independent-component-analysis%EF%BC%89/
