I know a lot of sources. I can't say for sure this is comprehensive because, of course, the sources have sources themselves. i360 is the name of the Koch brothers-funded or -run company that supplies lots and lots of data. The RNC data trust is clearly a large foundation where they're getting information or data from. There are indicators as far as field names go that L2 Political provided information, and I believe on Cambridge Analytica's website—not AIQ's website—they admit on their blog that L2 was the source.
Axiom was a source, I believe, that came out yesterday in Alexander Nix's testimony. When I group the AIQ and the Cambridge Analytica data together, there's so much interplay between the two that it's just intuitive that the datasets are intertwined, not to mention that clearly SCL IDs are in the field names of many of the imports.