forums.ps2dev.org :: View topic - PSP Multi Firmware Project
4 Ways to Downgrade a PSP - wikiHow Fun
How to Downgrade PSP Firmware - Nerd Bacon Magazine
How To] Downgrade Firmware on PSP Fat/Slim From 6.60 to 6.XX In Less Than 7 Minutes - YouTube
Cómo hacer downgrade de la PSP
I was trying to downgrade my PSP go to 6.20, but it warned me that the [Resume game] feature would be deleted. Does that mean I won't be able to use the
Downgrade PSP + Install OE(Chip Virtual)
Downgrading PSP 3000! - Instructables
How can I safely downgrade my Sony PSP firmware? - Ask Dave Taylor