U2's Bono undergoes back surgery - tour dates in doubt
One show already postponed after singer goes under the knife
U2 announce DVD release of 'YouTube' Rose Bowl gig
Band played to 97,000 people in the California stadium
U2 announce vinyl 'Artificial Horizon' remix album
Triple-disc edition will be released on May 14
U2 biggest earning act of 2009 in US
Bruce Springsteen, Madonna and Coldplay also raked it in last year, according to Billboard's Top 40 Money Makers list
U2 start work on new album
The Edge says they've got "something really special"
U2's Bono and Jay-Z record Haiti earthquake song
Singer and rapper combine for new material
'Hope For Haiti' telethon to be broadcast in the UK
Bono, Christina Aguilera, Justin Timberlake set to feature in George Clooney-organised charity appeal
George Clooney recruits Bono, Sting, Timberlake for Haiti benefit gig
Actor is organising US telethon for earthquake survivors
U2: We want to leave our mark on Glastonbury festival 2010
The Edge says he's got over scepticism about festival's 'hippy roots'
U2 score highest grossing tour of North America in 2009
Bruce Springsteen and Billy Joel also take in huge takings