The entire catalogue of the institutes’ periodical and book collections can be consulted via the National Library Service OPAC (On line Public Access Catalogue), to which both of the institutes of the service (Biblioteca d’Arte and Biblioteca Archeologica e Numismatica) contribute and participate.
http://www.biblioteche.regione.lombardia.it/vufind/Searchopacrl/Home
http://opac.sbn.it/opacsbn/opac/iccu/base.jsp

A good portion of the archive material is ordered and included in the catalogue of the region of Lombardy’s cultural heritage website. Reference cards can be found in the SIUSA portal (Unified Informations System of the Government Department for Archives) of the Ministry of Cultural Heritage, Activities and Tourism, in accordance with the respective national and international technical, descriptive and indexing standards.
http://www.lombardiabeniculturali.it/archivi/soggetti-conservatori/MIAA0...
http://siusa.archivi.beniculturali.it/