Executive Director, Medieval Studies Program, PhD, University of Toronto. Historian of the society and culture of Medieval and Early Renaissance Siena and Tuscany.
- The Magnates of Siena, 1240-1420. 2 vols
- Medieval and Early Renaissance Italy
- Manuscript Studies I: Paleography
- Manuscript Studies II: Diplomatics and Codicology
- Sexual and Economic Ethics in Medieval and Early Renaissance Italy
- Culture and Society of Medieval Seina
- Coedited The Blackwell Companion to the Middle Ages
- Enterprise and Liability in Sienese Banking, 1230-1350.
Medieval Academy of America, 1988
- Encyclopedia of the Medieval World. 2 vols.
- Coedited with Mark Meyerson: Christians, Muslims and Jews in Medieval and Early Modern Spain.
University of Notre Dame Press, 1999.
- Blackwell Companion to the Middle Ages
Blackwell, May 2009
- Edited: Mediaeval Studies, 1988-1990.
- Manuscript Studies I, 2009, 2012, 2014, 2015
- Manuscript Studies II, Spring 2009, 2012, 2012, 2015
- Medieval Latin (Fall 2008, 2010, 2012, 2014
- Lila Wallace/Readers Digest Visiting Professor, Harvard’s Villa I Tatti in Florence
January to June 2008