Thucydides set the standard for historical writing and is a central text both for Greek history and for historiography in general. This chapter focuses on three examples of surviving material from the ancient Mediterranean world, the works of Vergil, Sappho and the Res Gestae Divi Augusti, all of which have survived to the present day for different reasons. The process of restoring the 'correct' readings of a text is called textual criticism. It relies initially on the construction of a genealogical tree of relationships between manuscripts, based on the patterns of errors and variant readings contained therein. For printed materials, this means the appearance of text on the page. This has led to an effort to repurpose Adobe's Portable Document Format (PDF) as an archival digital format (PDF/A). Print-replicating technologies are typically argued to be preferable to others because they replicate the page structure of works, and therefore permit relatively precise citations to be made of their content.