Furthermore there are a lot of documents in Sunni books which say Shia are right. If you read historical books and some correspondence between scholars of Shia and Sunni, e.g. AlMurajiat or Nights of Pishavar you will simply find the truth. ValiAsr website has a lot of proof for Shia from Sunni sources.
Tabarani, a Sunni scholar says in his book Mujam AlOsat that prophet said: O Ali, you and your Shias are in the Heaven.