Because of the secretive nature of search scoring algorithms, it'll be hard to find a lot of hard science that is also current. Things change very quickly in the space, the best you can hope for are informed opines based on results. Those aren't going to be as rigorous as studies in academia, and since the described techniques actually work, they may not be freely available.
Deano’s answer to: “What research exists on the topic of SEO effectiveness?”
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