One thing that is really practical about Zagreb libraries is that when registering in one library, you actually register for 40 others (basically all the libraries in Zagreb) !

The Library's holdings and services are available only for registered users (fee is 40 kunas/year). You can register physically any of the libraries in the list below. When registering at a library, the librarian often fills the documents (see section below) for you. Do not panic if your OIB number has not come when you fill out those documents, it is possible to give it later in the semester.