There is a report available in Salesforce that breaks down customers by industry/vertical and current ATS:
https://gem-talent.lightning.force.com/lightning/r/Report/00OUT000002lB5J/view
The report only looks at customers over $30k ARR. Feel free to reference this report directly to search for the combination of industry & ATS that’s relevant for your prospect, and you can connect with the account owners directly to see if a specific customer would be a good reference. Hopefully this saves some of you a few round trips in terms of having to ask around for references that fit a certain criteria.
Please check with the account team for any of these customers before referencing them, even verbally. Some customers have very strict clauses in their contract that preclude us using their names or logos even on calls.