I have used a few books and articles to prepare for a talk, but I only used some of them directly in my slides. The slides also include parts that are made based my knowledge (background knowledge plus what I learned from reading those sources) but are not new information and could be found in those sources.
Should I cite all of those sources in my references slide? If yes, do I need to reference each piece of material on the slide, or just citing the sources at the end would be enough if I didn't use them directly?
NOTE My question is not a duplication this because that question is asking about referencing for presentation in general, but my question is not about referencing the sources I used directly, but those I read to build up my knowledge for the presentation but did not use directly.