A comment below asked about a notation in a particular passage in a book I referenced. As it turns out the book is fully searchable on Amazon. Myself, I do searches on google books, and if there isn’t a “view” of the book I’m looking for (or that page isn’t viewable), I will check for the book on Amazon. This covers a large proportion of the “fact checking” one might need to do. Also, google scholar is pretty well integrated with books, so you might just want to start out there. Here are the libraries who have signed on to google books, so you can imagine that the coverage is pretty good.