If you can't find the book or article you are looking for, please send an email with a purchase proposal to:
Madeleine Bergquist
Librarian
madeleine.bergquist@khm.lu.se
The library catalogue
Internet Archive is a non-profit library of millions of free books, movies, software, music, websites, and more.
For example Guggenheim just released a collection with digitized art books.