Risen from the dead: PSP Firmware 6.61 is now available! - Wololo.net
Guide How to UPDATE to Latest Firmware 6.61 For PSP and How to Fix Error Update 9.90 | Guide How to UPDATE to Latest Firmware 6.61 For PSP and How to Fix
PSP: Custom Firmwares for Firmware 6.61 possible - Currently being updated! - Wololo.net
Update to 6.61 Infinity? : r/PSP
Tutorial : install 6.61 Pro c2 cfw - YouTube
PSP: First hacks for the new Firmware 6.61 - PRO CFW & Downgrader updated! - Wololo.net