Here are some of the best reference books that I have found relating to finding legitimate Literary Agents to submit your work to.

Guide to Literary Agents 2020:

The Most Trusted Guide to Getting Published (Market)

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Why I would recommend this book:- No matter what you’re writing – fiction or nonfiction, books for adults or children – you need a literary agent to get the best book deal possible from a traditional publisher. In this volume, Robert Lee Brewer collates details of Literary Agents based in the US and internationally for hundreds of literary agents who represent writers and their books. It also contains a wealth of other information on how to position your work with agents in the best possible manner.