Down East Books. p. 550. ISBN 978-0-89272-902-9. ↑ Summary of a Finnish government report (1992) on silencers, muzzle brakes and noise levels[permanent dead link] ↑ (in German and English) Schalldämpfer = Gehörschützer für Jäger, data collected on noise levels Archived 28 March 2009 at the Wayback Machine ↑ "More About: Shooting/Hunting Hearing Protection". www.earplugstore.com. ↑ Tilstra, Russell C. (2011). Small Arms for Urban Combat: A Review of Modern Handguns, Submachine Guns, Personal Defense Weapons, Carbines, Assault Rifles, Sniper Rifles, Anti-Materiel Rifles, Machine Guns, Combat Shotguns, Grenade Launchers and Other Weapons Systems.