1. 1981.The Young Correggio and his Leonardesque Sources23–26. New York: Garland Publishing lnc. This portrait, now considered at least partly autograph, was reworked by a later hand. For a brief outline of its genesis see David Alan Brown, (pp.For an illustration in colour, see Rosaline Bacou,Great Drawings of the Louvre Museum: The Italian Drawings(New York: George Braziller, 1968), No.14
2. Fischer, Chris. l990.Fra Bartolommeo: Master Draughtsman of the High Renaissance137–9. Rotterdam: Museum Boymansvan Beuningen. For the interest of Fra Bartolommeo in Leonardo see, for example, E.Fahy, “The Early Work of Fra Bartolommeo,”Art Bulletin, 51 no. 2 (1969). 142–154
3. Monnier, G.Pastels from the 16th to the 20th Century13 For Leonardo's portrait, see (Geneva: 1984), p.;also G. Monnier, “Pastel: Its Genesis and Evolution to the Twentieth Century,” inDrawing Masters and Methods: Raphael to Redon, D. Dethloff (London: 1992), p. 159. For Fra Bartolommeo's study, see Fischer, ibid.; the medium of the heightening is identified as yellow chalk only on p. 26
4. Watrous, James. 1957.The Craft of Old Master Drawings91Madison: University of Wisconsin Press. (These are not pure minerals but amorphous compositions containing clay