The work of historians of economic ideas is often supposed search for predecessors of an established truth, or sometimes to denounce its ideological bias. In this note it is argued that it should be approached as a genuine effort to unravel the past and that the study of documents, correspondence and unpublished material should be essential ingredients of this work. The microfilms of the papers of R.F. Kahn, J. Robinson and N. Kaldor - made available by the Bank of Italy in collaboration with the Archives of the King's College, Cambridge - offer an extraordinary opportunity for a scholarly investigation into the multifarious aspects of the Cambridge School of Economics. As part of a broader project to recover and enhance its collection of scientific literature, the Library of the Bank of Italy has recently acquired the Nicholas Kaldor and Richard Kahn archives on microfilm and will shortly be adding those of Joan Robinson. The Library aims at acquiring missing volumes through purchases in the antique market and lithographic reproductions; a new catalogue of the acquisitions made during the period 1894-1965 is being compiled as a step towards a general computerized catalogue.