University Professor Emeritus University of Pittsburgh
I taught at Yale University from 1965 to 1975, and was subsequently Director of the Jewish Studies Program at the University of Pittsburgh from 1973 to 1991. I retired from Pitt in 1999 after having been promoted to University Professor. I was a Guggenheim fellow in 1975.
Ibn al-Muthannâ’s Commentary on the Astronomical Tables of al-Khwârizmî. Two Hebrew versions, edited and translated, with an astronomical commentary. New Haven: Yale University Press, 1967.
The Astronomy of Levi ben Gerson (1288–1344). New York: Springer-Verlag, 1985.
Astronomy in the Iberian Peninsula: Abraham Zacut and the Transition from Manuscript to Print. Transactions of the American Philosophical Society, 90.2. Philadelphia: American Philosophical Society, 2000 [with José Chabás].
“Levi ben Gerson and the cross staff revisited”, Aleph, 11 (2011), 365–383.
“A table of new moons from 1501 to 1577 in a Hebrew fragment preserved in the John Rylands Library”, Aleph, 13 (2013), 11–26.