The Internet Archive is interested in creating a wishlist of books to prioritize for digitization and they reached out to ask if we have data of ISBNs cited in WIkipedia.
Back in 2015 @Halfak and I worked on this dataset which hasn't been refreshed since then.
The goal of this task is to publish a fresh snapshot of this data using the mwcites utility and potentially expand the dataset to some of the largest language editions by article count, other than EN (i.e. FR, SV, DE, NL, RU, IT, ES, not including bulk populated editions such as Cebuano).