The Historic Texts Collection brings together an extensive collection of primary sources for the history of Late Antiquity and the Western Middle Ages as well as selected commentaries and reference works. The collection is located in the Starr Main Reference Room of Sterling Memorial Library. For a quick overview of all titles, search for "SML, Linonia & Brothers, Historical Texts" (in quotation marks) in Quicksearch. From there you can filter by language, location, genre, although keep in mind that cataloging in these areas is not consistent. The collection in Starr is meant to be browsed in person.
A list of all the titles currently in Starr (but also including duplicate copies at the Classics Library, Divinity Library, the Beinecke Library, or shelved offsite) is here.
The following links will retrieve the series and individual items held in Starr. To find items in these series held throughout the Yale Library system (including online access when available), click on an individual title, and from there click on the series title in the record. Two major multi-part series, the Corpus Christianorum and the Monumenta Germaniae Historica, are listed in separate boxes on the left.