For people wondering, Chris Voss is the former lead international kidnapping negotiator for the FBI. Here's a podcast where he talks about negotiation [0] and the link to the book the above comment refers to [1]. His talk at Google about the same subject might be interesting too [2].
[0] https://fs.blog/2018/01/chris-voss/
[1] https://www.goodreads.com/book/show/32444582-never-split-the...