zydeco: Korchnoi points to lots of mistakes in this game.
He thinks 9.Re1 is better than 9.a3.
9....Nxc3 is an overanxious attempt to punish white for 9.a3.
Korchnoi says that 11.Rb1 is superficial, and Larsen was best off playing in the center with, say, 11.Bb2, 12.Bc2, and 13.e4.
More proof that I'm not a grandmaster: I thought 16....Ra7 was a nice subtlety. Korchnoi says that it was a weak move, which he recognized as weak, and played "only to give Larsen the uncomfortable feeling that he'd made a mistake." 16....Rab8 was better.
Larsen thought that 17.h4 was 'the initial cause of his defeat.'
21....Nb7 was better, to transfer the knight to d6.
Korchnoi says 24.Bd2 was the critical mistake. White had to play 24.Bd3.
26.e4 was white's best chance.