Daniel A. Di Liscia (Ph.D. 2003), is Lecturer at the Ludwig-Maximilians-Universität München (Germany), at the Munich Center for Mathematical Philosophy. He worked on the edition of Copernicus and Kepler, and published several papers on the Oxford Calculators, in particular on the latitude of forms. Edith D. Sylla (Ph.D. 1971) is Professor Emerita at North Carolina State University (Raleigh, North Carolina). She works on the history of mathematics, physics, and their interrelations from the late Middle Ages to the early eighteenth century.