What makes a publication (or a publishing forum) academically acceptable for inclusion in a literature review? I'm in the process of conducting a systematic literature review and an integral part of this is the definition of inclusion and exclusion criteria for filtering the search-result-publications.

A common criteria for these reviews is that the publication is an academic publication or otherwise academically acceptable. I haven't been able to find a proper definition for this. The ones that I can think of are that the publication fora must exercise peer-review on the papers and that the fora are widely accepted by (inter)national funding agencies.

Hence, my question is what makes a publication or a publishing forum academically acceptable?
I am afraid this is an impossible question to get right: An "acceptable academic publishing forum" would be one that is accepted by "acceptable academics" - and "acceptable academics" would be identified by publishing in "acceptable academic publishing fora"...

Peer-reviewed is not a bad criterion, but it falls short: There are peer-reviewed journals for creationists and homeopaths - so the value of peer-review depends crucially on who the peers are. It doesn't even work as a necessary criterion, as missing the arXiv for math-y fields or books for humanities would mean that a literature review is very incomplete.

"Acceptance by funding bodies" gets the question backwards: Funding bodies try to approximate what the academic community considers good publication venues, they don't define it.

If formal inclusion/exclusion criteria are important for you (maybe because you do some meta-statistics?), you will need to look for field-specific standards. In medical subjects, I could imagine that "listed on pubmed" would be an acceptable one. In this case, looking are published meta-studies and their criteria would be useful.