I think this is a fair topic to bring up. Between commercial textbooks and freely-distributed PDFs, there is a huge amount of expositional material for any give

I think this is a fair topic to bring up. Between commercial textbooks and freely-distributed PDFs, there is a huge amount of expositional material for any given topic in sub-research level mathematics and one does wonder whether there could be a better method of clustering and ranking the material. (Clustering is probably very doable.)