Upgrading PSP OFW 3.90 to 6.61 without a battery : r/PSP
Updating The PSP System Software to 6.60 / 6.61 - pspunk
PSP Firmware Update 6.61 | GBAtemp.net - The Independent Video Game Community
PSP update: 6.61, firmware, PlayStation
Tutorial] Install PSP 6.61 Pro-C Infinity Custom Firmware | Page 2 | GBAtemp.net - The Independent Video Game Community
PlayStation Portable system software - Wikiwand
PSP update: 6.61, firmware, PlayStation
PlayStation Portable (PSP) 6.61 firmware download
Complete Guide to PSP Custom Firmware | ReviveToday
4 Ways to Upgrade Your PSP Firmware - wikiHow
Psp Filer 6.61 Free Download
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 6.61 Custom Firmware Install on any PSP - PSP, PSP Slim, PSP 3000, PSP Go & E1000 | Digiex
Sony PSP receives random firmware update - SlashGear