is Professor of Italian Renaissance painting and sculpture at Columbia University of New York. Since 1992 he is the president of ArtWatch International. He is one of the main expert of the Italian Renaissance, in particular of Jacopo della Quercia, Masaccio, Raffaello and Michelangelo. He is the author of many articles and books as: Michelangelo: A Lesson in Anatomy (1975); Raphael (1976; ed. italiana 1983; ed. tedesca 1984); Masaccio: The Documents, in collaborazione con Gino Corti (1975, ed. italiana 1985); Leonardo's Rules of Painting: An Unconventional Approach to Modem Art (1979); Italian Renaissance Painting (1981) Revised and expanded edition, in English, French, German, Italian, 1999-2001; The Doors of the Fiorentine Baptistry (1985, inglese, italiano e tedesco) Jan Sawka. A Book of Fiction, Introduzione (1986); Raphael Before Rome, cura e introduzione (1986); The Sepulchral Monument for Ilaria del Carretto by Jacopo della Quercia (1988 e 1989, ed. italiana e inglese); Jacopo della Quercia (1991); The Tyranny of the Detail. Contemporary art in an urban setting (1992); Raphael. The Camera della Segnatura (1993); The Three Worlds of Michelangelo (New York, 1998) (German, Korean, and Polish editions); Masaccio, a Monograph (2002). For European Press Academic Publishing, he published the Italian edition of his book on art restoration and scandals L'Arte Violata (2002) and From Duccio to Raphael. Connoisseurship in Crisis (2006).