PSP 6.61 Custom Firmware Install on any PSP - PSP, PSP Slim, PSP 3000, PSP Go & E1000 | Digiex
Infinity 2.0 released for the PSP, allows for persistent CFW on all models of PSPs on 6.60 and 6.61 | GBAtemp.net - The Independent Video Game Community
PSP Official Firmware | ReviveToday
4 Ways to Upgrade Your PSP Firmware - wikiHow
Updating The PSP System Software to 6.60 / 6.61 - pspunk