Hey everyone. Medical resident here who has been working on revising a book chapter. My task is to try and update the sources within the chapter while also making it more concise. My PI (not sure if that's even the right term) would like articles published within the past 5 years which has been challenging. Wanted to ask if secondary sources like systematic reviews, meta analyses, etc are okay to use as a form of citation? I find the paper and then will look and see what they are citing and will read that as well but the original citation tends to be a bit older. Not many studies have been published recently and most of the medications have been around for a while. Previously had only done clinical research and case reports so I don't have experience with writing/revising a textbook. Thanks!