We present the outcomes of the Linked Books project, resulting in a prototype citation index interlinking the Italian national library catalog (Opac SBN) with the information system of the State Archive of Venice and international authority records or “metaengines” such as VIAF.org and Europeana. Our prototype includes 3.850.581 citations extracted from a corpus of 2.475 volumes, of which 1.905 monographs, and 552 journal volumes, or 5.496 articles therein. The corpus is focused on the history of Venice. The Linked Books project allowed us to explore the feasibility and desirability of a citation index for the humanities, and to face and solve technical challenges including: the selection of a thematically representative corpus from bibliographic resources and expertise, the digitization of these materials within the bounds of copyright, the automatic extraction of citations and the development of public search interfaces.