https://blog.wongcw.com/2021/01/27/%e5%8d%8a%e5%84%84%e5%83%8f%e7%b4%a0%e5%8f%af%e6%8b%8d8k-%e7%b4%a2%e5%b0%bcalpha-1%e5%85%a8%e7%95%ab%e5%b9%85%e5%be%ae%e5%96%ae%e7%99%bc%e5%b8%83/