zydeco: One that gets away from Ivkov.
Portisch has an interesting opening innovation (16.a5 and 17.Ra4!?) but then goes wrong with 20.Bg4? (Maybe he was trying to get the same kind of setup that Spassky used against Unzicker in round 2).
Ivkov is winning a pawn at a minimum after move 26 but prematurely simplifies to the endgame.
35....Nf6 is part of a failed combination. He calculated as far as move 41 but thought that whit was forced to play 41.Rd8+ when 41....Ke7 wins.
Ivkov turns out to be entertaining - and something of a loose cannon - as an annotator. Here's his Gentleman's Guide to Chess and Women:
20.Bg4? "Based on positional principles the move would not be bad. But a chess game is the same as a woman - you must never approach it with any prejudices or dogmatically. One must always take into account the dynamics of the position, its whims and peculiarities in the most innocent-appearing situations."