1. V. Biringuccio, in: C.S. Smith, M.T. Gnudi (Trans.), The Pirotechnia of Vannoccio Biringuccio, Dover, New York, 1990, pp. 419–420.
2. Muzzle wear of cannon
3. G.L. Shulyer, Bur. Ordnance Memo S72-4/11/77, December 1928.
4. R.E. Kent, BRL Report No. 133, US Army Ballistic Research Laboratory, Aberdeen Proving Ground, MD, March 1939.