https://myvanlife.com/2011/12/02/vow-of-silence%ef%bc%8c%e6%9c%89%e9%97%9c%e4%b8%89%e5%80%8b%e5%8d%81%e4%ba%8c%e6%ad%b2%e7%9a%84%e7%94%b7%e5%ad%a9/