1. Richter, J. P. 1939.The Literary Works of Leonardo da VinciVol. 1, 359London: Oxford University Press.
2. Watrous, J. 1957.The Craft of Old-Master Drawings118Madison, WI: The University of Wisconsin Press.
3. 1821.Lehrbuch der Lithographie und des Steindruckes172–175. Munich Formulas for Senefelder's crayons may be found in his book