it is hard to determine the scale of such access, and, in any event, there are significant limits on this approach. Along with the challenge (and expense) of reaching agreements with relevant rightsholders, there is also the practical difficulty of simply identifying and finding the rightsholder that one must negotiate The vast majority of in-copyright books are out-of-print or out-of-commerce, and most are not actively managed by their rightsholders. There is no official registry of copyrighted works and their owners, and existing datasets can be incomplete or erroneous. As a result, there may be no way to license the vast majority of in-copyright books, especially those that have or have had limited commercial value. Put differently, the barrier to using most books is not simply to pay publishers; even if one had significant financial resources, licensing would not enable access to most works.