I originally assembled the material in this volume for my own use, as an aid to the restoration of damaged texts. Living for years as slips of paper in several shoeboxes, it assumed its present form in the academic year 1994/5 thanks to two grants from the University of Illinois at Urbana-Champaign. These grants, the first from the Research Board of the Graduate College, the second from the Center for Advanced Study, released me from teaching and provided the impetus to construct the present work. I am most grateful to the University for its support.
