„Cannons and Gunpowder“ (mysite.du.edu) «Cannons and Gunpowder» http://mysite.du.edu/~jcalvert/tech/cannon.htm „Cannons and Gunpowder“ (mysite.du.edu) http://mysite.du.edu/~jcalvert/tech/cannon.htm Gunpowder & Cannon (Calvert; detailed)