Digital Collections

In times of closed research libraries and the more or less compelled transfer to home office an overview of some important sources of freely accessible digital collections of both books and journals might be useful:
The Directory of Open Access Books
The Directory of Open Access Journals
Torrossa open (Casalini Full Text Platform)
The Art Discovery Group Catalogue (narrow your search to Open Access content)
Getty Research Portal (for digitized rare book collections in art libraries)