Karpova: Schiffers and Saburov played several games <zur praktischen Erläuterung der "Spanischen">, hence the event "Ruy Lopez research".On 4.Bxc6, the annotator notes that Black's position is usually cramped in the 3...d6 variation. 4.Bxc6 gives his ♖ freedom of action on the b-file and the ♗ on the a6-f1 diagonal, while White gives up the ♗ pair, in addition.
6.Nh4 threatens <Qh5+>, planning <0-0> and <f4>.
7.d5 was not annotated, but I wonder why not 7.0-0 ?
The annotator notes that Black could have played <24...h6 25.Bxh6 f4>. It was also possible later, 26...h6.
28.Qb3 looks weak. Perhaps, White should have tried to invade with his ♖ and played 28...Rd8.
Black may have tried 35...h6.
Black is winning anyway, but even stronger than 41...Rg2+, was 41...Ra1+ (42.Kf2 Rf1+ 43.Kg3 Rg1+, if 43.Kxf1 checkmate follows after 43...Qd3+ with ♕ and ♗ working together).
Source: 'Wiener Schachzeitung', May-June 1906, pp. 177-178