Conducting a literature review, what period should the papers be taken from?
The year that a paper was published is entirely irrelevant to the question of if it is worthy of inclusion. I’ve read good review papers citing work that is almost three thousand years old and I’ve read good review papers not citing anything older than 2001. Using age as a proxy for relevance is an incredibly poor decision. You should include what is important for someone in the field to know, regardless of when it was published.