In the general catalogue is available bibliographical references of all documents held in the library: books, manuscripts, newspapers, graphics, music, audio-visual and sound records.
Links of interest
Sets of catalog data in open formats and reusable (BNElab)
The BNE made available to the citizenship semantizado its catalogue, applying technologies of the semantic Web.
Catalog data are under the licence CC0, so it is free and does not require prior permission