[13] Kleck, op. cit., pp. 104-108; Kopel, op. cit., p. 423; Edgar A. Suter, "Guns in the Medical Literature - A Failure of Peer Review", The Journal of the Medical Association of Georgia, Volume 83, (March, 1994), pp. 133-148. The frequency of defensive handgun use by civilians in the United States has been conservatively estimated at 645,000 times per year, an average of once every 48 seconds.