At Archives & Special Collections you can find a number of 16th and 17th century primary source materials that Shakespeare referenced for many of his works, including Macbeth, King Lear, Cymbeline, and King John, just to name a few. In addition, Archives & Special Collections has a number of 17th and 18th century materials on British history, as well a number of Shakespeare's early works and criticism.
This section of the library guide focuses on Holinshed's Chronicles of England, Scotland, and Ireland, Foxe's Book of Martyrs, The Anatomy of Melancholy, and additional sources related to Shakespeare's plays.