See R. Bernheimer, “The Martyrdom of Isaiah,” Art Bulletin 34 (1952), pp. 19–34; on the identification of all the just, see Robert W. Gaston, “Iconography and Portraiture in Bronzino’s Christ in Limbo,” Mitteilungen des Kunsthistorischen Instituts in Florenz 27 (1983), pp. 41–72.
