Ulhumbrus: After 22...Rc8 Donner wants to play 23...Qb8 and 23...Rc7 to defend his backward a pawn. According to Petrosian the move 23 Bd5!! wins the game.
The move prepares to exact a price for Black's carrying out of Black's plan.
On 23...Qb8 24 Bxe6! Black's Rook on e7 is overworked. If it has to defend the a7 pawn it cannot also recapture on e6 and the alternative recapture 24...fxe6 leaves Black with a doubled isolated e pawn.
After 24...fxe6 according to Petrosian <...White's victory is now a matter of a proper plan that should consist of the following: advancing the h pawn not only to break up Black's position on the king side, but also to get at the bishop. It is clear that White at the proper time, by exchanging bishops, can without difficulty take care of the Black e pawn.> I assume that the e pawn which Petrosian refers to is not the e6 opawn but the e5 pawn which is defended by a minor piece, Black's B.
After 46 Re4 according to Petrosian < White can win easily by combining threats to the king with the possibility of winning one of the pawns>
At the end Petrosian's comment on 55 Rf6, in reply to which Donner resigns, is <Black resigns since after 55...Rd7 there could follow 56 Qe4 Re7 57 Rf8+ Kc7 58 Qa8>
In the sequence above after 56 Qe4 the Black Rook on d7 is overworked. If it goes to the e file in order to defend the e6 pawn it cannot then use the d file to go to d8 to defend the King in reply to 57 Rf8+ which begins a mating attack.