Manchester City manager Pep Guardiola has said he is "curious" about teams that have won a treble as his side bid to claim an unprecedented quadruple.
Manchester United are the only English side to ever win the Premier League, FA Cup and UEFA Champions League in the same season.
They achieved the feat under Sir Alex Ferguson in 1999, and Guardiola did the same in Spain with Barcelona 10 years later when the Blaugrana won La Liga, the Copa del Rey and the Champions League.
In 2012-13, the season before Guardiola took over, Bayern Munich became Germany's first-ever treble winners.