Lavin, Irving, “Divine Grace and the Remedy of the Imperfect: Michelangelo's Signature on the St. Peter's Pietà," in Nicole Hegener, ed., Künstlersignaturen von der Antike bis zur Gegenwart/Artists' Signatures from Antiquity to Present, Petersberg, 2013, 114-151. Updated version in artibus et historiae, no. 68, 2013, 277-328.
