While our research concentrates on printed editions of Euclid up to 1700, it bears mentioning that the Bodleian Library at the University of Oxford is home to some spectacular Euclid manuscripts. Among them is MS. D’Orville 301, written in 888 by the scribe ‘Stephanos the clerk’ with annotations added between 10th and 14th centuries. It is based on the Elements edited by Theon of Alexandria in the 4th century. Here is a detail of the Pythagorean theorem on the verso of folio 31; click to view it on the Digital Bodleian website.