The word for the material papyrus is also used to designate documents written on sheets of it, often rolled up into scrolls. The plural for such documents is papyri. Historical papyri are given identifying names—generally the name of the discoverer, first owner or institution where they are kept—and numbered, such as "Papyrus Harris I". Often an abbreviated form is used, such as "pHarris I". These documents provide important information on ancient writings; they give us the only extant copy of Menander, the Egyptian Book of the Dead, Egyptian treatises on medicine (the Ebers Papyrus) and on surgery (the Edwin Smith papyrus), Egyptian mathematical treatises (the Rhind papyrus), and Egyptian folk tales (the Westcar papyrus). When, in the 18th century, a library of ancient papyri was found in Herculaneum, ripples of expectation spread among the learned men of the time. However, since these papyri were badly charred, their unscrolling and deciphering is still going on today.