The quality of sources is more important than the quantity. Make sure your sources come from reliable academic publications that are peer reviewed. This will increase the credibility of your writing. It is better to have 10-15 quality sources, for example from peer-reviewed academic journals or books, rather than 20-30 sources that are from blogs, websites or other not-reviewed-by-experts publications. There is no fixed number of sources that you need to use. Just focus on questions, aspects and discussions in the field, not the number. I hope it helps.
