The British Library catalogue of additions to the manuscripts :
the Blenheim papers.
APA Citation
British Library. Department of Manuscripts. (1985). The British Library catalogue of additions to the manuscripts: the Blenheim papers. London: The Library.
MLA Citation
British Library. Department of Manuscripts. The British Library Catalogue of Additions to the Manuscripts: the Blenheim Papers. London: The Library, 1985.
Warning: These citations may not always be complete (especially for serials).