http://www.gamewinners.com/playstation/GranTurismo.htm

http://www.consolecheatcodes.com/psone/granturismocheats.html

http://www.askcheats.com/cheats/PSX/Gran-Turismo.html

http://www.consolecheatcodes.com/playstation2/granturismo3cheats.html

http://cheats.ign.com/ob2/068/489/489327.html

http://cheats.ign.com/ob2/068/682/682963.html

http://www.cheatcc.com/psx/codes/gt2.html

http://www.cheatcc.com/ps3/granturismo5prologuecheatscodes.html

http://www.cheaterzclub.com/grandturismo4ps2.shtml

http://vgstrategies.about.com/od/ps2cheatscodesg/a/gt3aspeccheats.htm