laskereshevsky: Assuming that the white is maybe not winning, but already enough on the edge, after 20. ♙g5... logically must be searched an improvment for the Black before this point...Without giving many variations, (first because i want to follow the "not forced lines moves but ideas first" Capablanca's and Lasker's advice, and last but not least because in this period im too much lazy...) i noticed that maybe the rook a8 arrived in c8 too late. I suggest to play 16. ... ♖ac8 in place of 16. ... ♙b4
Beside the correct <tbone>'s suggestion ♙h6 and ♖d8 wich are not so charming moves ( but more or less not so bad at all ), i have same doubt about the effectivness of 18. ... ♕c5.
the White♕ was forced to place herself in a good square g2, taking "contact" with the open H line, putting pressure on the G line almost forcing the not great move ♙g6, and supporting the ♗f3 on the great h1-a8 diagonal...
Its a fantastic offensive-defensive placement, i dont think its worth to give all this to the white in change of the Black centralized ♕...
Its a well know fact that when i force my opponent to do a move he would like to do it, I just lost a tempo.
More, when the white♘ moved to the absolutly essential d3 square, the Black lost another vital tempo... Maybe, adding all those not really mistakens, but innacurancyes by the black, ♖d8, ♙h6, ♙b4, ♕c5, we found the "Larsen's mistake"!...
(♙g6 is not nice, but IMHO almost forced, so we cant consider it a real bad choice)
P.S.: not yet checked, the main line in case the Black accept the ♗g5 sacrifice... But I could believe in a grand-master like Kavalek Judment.. (Did U see?! another pragmatic actitude in a tipical Lasker's style by my side...:) )