Without libraries, museums would be flying blind. We rely on our fellow information hoarders professionals to help us solve problems, guide us to resources, and occasionally go for a drink. In so many ways, libraries are the left to our right, and one of the places this relationship is most visible is provenance research.
Provenance research used to be a much more labor-intensive affair. Auction catalogues, travel diaries, and other archival material were held by a few libraries, and if you could figure out which repository had the material you were looking for, getting access was another issue entirely. Many books and papers were held in closed holdings that could only be accessed by appointment and by application. The researcher then had to travel to the library, get the book, maybe do a translation, and do the research.