Although I am just in the beginning of my quest for negotiating resources, here are some of my favourite go-tos.

This is a classic that I regularly turn to in tension filled situations. This outlines some of the basic tenants of getting to the heart of the issue, and separating what is said from the intent. It also provides some great tools and strategies on how to communicate your thoughts in a neutral way.

Pink spends the first few chapters of this book explaining the importance of being genuine and that selling is involved in most people’s jobs – even if you are not in a traditional sales environment. The importance of being able to move people and negotiate with others is becoming a sought after skill set.
Pulling from diverse resources, the second half of this book is where he introduces some helpful tools for communicating effectively, determining who the decision makers in the room are, and how to keep motivated during a negotiation grind.

This book is actually a part of a larger Harvard project. It comes from the same project as the book Difficult Conversations. In Getting to Yes, the authors delve into the importance of focusing on the underlying interests in positions, and separating the people from the problem itself.
One of tools I have taken from this book is utilized when presenting proposals. The authors suggest beginning with your rationale before presenting the solution. Leading with the logic is more likely to engage your counterpart rather than giving them the opportunity to begin the conversation with a yes/no decision.