zydeco: Larsen writes that he was feeling sick and wanted only to draw. The fact that Ivkov still managed to lose is indicative of his horrible form in this tournament.
Ivkov says that he was surprised by 15.gxf3!
All the opening moves were repeated a few rounds later in Reshevsky vs Ivkov, 1966 although Ivkov deviated in that game with 18....Kg7. Larsen had planned a piece sacrifice with 19.f4 c6 20.fxe5 cxd5 21.exd5.
Ivkov thought he had a devastating pin on white's knight with 21....Rd8 but completely missed that white breaks the pin with 22.Rd1.
Ivkov thought he was in a lost position by move 30.
Here is Ivkov's note to 35....Kf8! "In annotating the previous game I mentioned that no one is spared from errors due to inverting moves, but that this happens very rarely. But it happened to me in this game as well as before with Unzicker. In time pressure I had already "played" 37....c5 expecting the variation 38.Nd5+ Kf7 39.Nb6+ c4 40.Nxc4 Nxc4 41.Bxc4+ Kg6 considering it sufficient for equality. What happened, however? I actually played immediately 37....Kf7!? and a unique tragicomic situation occurred with a grandmaster putting his own king under the attack of his opponent's bishop! Larsen looked at me queerly, but in the following fraction of a second we understood each other. I corrected myself immediately and put the king on f8."
The irony is that the accidental move 37.....Kf8 is much better than Ivkov's intended 37....c5. Instead of 39.Nb6+, Larsen could have played 39.Kd3 winning. With 37....Kf8, Ivkov had a draw if only he'd played 40.....Nxd5 41.exd5 Ke7. Instead, he blundered right before the time control with 40....Nd7.
42....Nd8 was a blunder occurring right after resumption.
47...Nb8 produced a study-like position.