Book excerpt: Letter writing was the major branch of rhetoric in the High Middle Ages (ars dictaminis) and Renaissance (ars epistolandi). As the primary source of discourse it played major roles in the history of education, the Latin language and literature, and its relation to grammar and oratory (ars arengandi). The letters are also a very rich source ranging from Church and State correspondence to social hierarchies and fiction. Several hundred authors, recognized as precursors of the Humanists, produced treatises, manuals, formularies and model letter collections found in a few thousand largely unstudied manuscripts. This is the third and final volume of the Medieval and Renaissance Letter Treatises and Form Letters, a singular reference work, a manuscript inventory of texts, most of which were examined in situ by Emil J. Polak in almost nine-hundred libraries and archives. The repertory is arranged alphabetically by country and city with standard details for each manuscript. Four indexes conclude the work.