Frankly wrote on 01/02/07 at 13:19:52:

Thanks - the Korchnoi line is the one cited in a footnote in the 14th Edition of Batsford Modern Chess Openings (although the game cited is de Firmian-Hellers 1989).

But, instead of 16Rad1, Fritz has 16 Nf6+!? which looks a bit scary for Black, although I have not come across a recorded game with it - save that I played against Fritz (set to an appropriate rating of course) and lost as Black.

i.e. 13Ne4 Be7 14. Be3 Nf5 15 Qc2 0-0 and then, anything but Rad1 (such as Nf6+).

I have found the following games with 16.Nf6+

Viktor the terrible defended it comfortably enough

**[Event "Sarajevo"]**

[Site "Sarajevo"]

[Date "1984.??.??"]

[Round "?"]

[White "Van der Wiel, John TH"]

[Black "Kortschnoj, Viktor"]

[Result "1/2-1/2"]

[ECO "C80"]

[WhiteElo "2515"]

[BlackElo "2635"]

[PlyCount "90"]

[EventDate "1984.03.??"]

[EventType "tourn"]

[EventRounds "13"]

[EventCountry "YUG"]

[EventCategory "12"]

[Source "ChessBase"]

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Nxe4 6. d4 b5 7. Bb3 d5 8. dxe5

Be6 9. Nbd2 Nc5 10. c3 d4 11. Bxe6 Nxe6 12. cxd4 Ncxd4 13. Ne4 Be7 14. Be3 Nf5

15. Qc2 O-O 16. Nf6+ Bxf6 17. Qxf5 Be7 18. Rad1 (18. Rfd1 Qc8 19. Rac1 (19. b3

c5 20. Qe4 Rb8 21. Ne1 Qb7 22. Qxb7 Rxb7 23. Rac1 Rc7 24. f4 g6 25. Nf3 c4 {

1/2-1/2 Thipsay,P (2475)-Prasad,D (2445)/Sakthi 1996/CBM 053}) (19. Qe4 c5 20.

a4 c4 21. h3 Rb8 22. axb5 axb5 23. Ra7 Bc5 24. Bxc5 Nxc5 25. Qd5 Nd3 26. Nd4

Nxb2 27. e6 Nxd1 28. exf7+ Kh8 29. Ne6 Ra8 30. Nxf8 Rxa7 31. Nd7 Ra1 32. Kh2

Ne3 33. fxe3 Rf1 34. Ne5 g6 35. Qd4 Qc7 36. g3 Kg7 37. Nxc4+ Kxf7 38. Qd5+ Kg7

39. Qxb5 Rf2+ 40. Kh1 Qxg3 {

0-1 Barendse,T (2206)-Ernst,S (2474)/Wijk aan Zee 2004/CBM 099}) 19... Rd8 (

19... c5 20. Qe4 Qc7 21. Ne1 Rfd8 22. f4 Rxd1 23. Rxd1 Rd8 24. Rd5 Qc6 25.

Rxd8+ Nxd8 26. Qxc6 Nxc6 27. Kf2 g5 28. Kf3 Kg7 29. Ke4 gxf4 30. Bxf4 Kg6 31.

Nc2 Nd8 32. g4 Ne6 33. Be3 Bg5 34. Bf2 h5 35. gxh5+ Kxh5 36. b3 Kg4 37. Ne1 Kh3

38. Kd5 c4 39. bxc4 bxc4 40. Kxc4 Kxh2 41. Nf3+ Kg2 42. Nxg5 Nxg5 43. Bh4 Nf3

44. Bf6 Kg3 45. a4 Kf4 46. Kd5 Kf5 47. a5 Kf4 48. Bh8 {

1/2-1/2 Morgado,J (2275)-Romero,L (2096)/Buenos Aires 2003/CBM 097}) 20. Rxd8+

Qxd8 21. Qe4 c5 22. b3 Ra7 23. h3 (23. g3 g6 24. Kg2 Kg7 25. h4 h5 26. Rc2 Rd7

(26... Rc7 27. Nd2 Rd7 28. Qc6 Nd4 29. Bxd4 Rxd4 30. Ne4 Rd1 31. Nxc5 Qd4 32.

e6 Bxc5 33. Rxc5 Rd2 34. Qf3 Qxc5 35. Qxf7+ Kh8 36. Qe8+ {

1/2-1/2 Zarnicki,P (2540)-Rosito,J (2420)/Pena City 1996/CBM 055 ext}) 27. Qc6

Rd1 28. Rd2 Rxd2 29. Nxd2 Nd4 30. Bxd4 cxd4 31. Ne4 d3 32. Nd6 f6 33. Qd5 Qg8

34. exf6+ Bxf6 35. Qxd3 Qe6 36. Ne4 Be7 37. Qd4+ Kh7 38. Nd2 Qc6+ 39. Qe4 Qd6

40. Nf1 Kg7 41. Ne3 Bf6 42. Qb7+ Kh6 43. Qf7 Qc6+ 44. Nd5 Bg7 45. Kh2 Qc2 46.

Ne7 Kh7 47. a3 a5 48. a4 bxa4 49. bxa4 Qe4 50. Kg1 Qe1+ 51. Kg2 Qe4+ 52. Kh2

Qc2 53. Qf4 Be5 54. Qf7+ Bg7 55. Qf4 Be5 56. Qe3 Bg7 57. Qb6 Qe4 58. Qd8 Qxa4

59. Qg8+ Kh6 60. Qf7 Qc2 61. Ng8+ Kh7 62. Nf6+ Kh6 63. Ng8+ {

1/2-1/2 Rodriguez Cespedes,A (2520)-Sorin,A (2505)/Matanzas 1995/CBM 048})

23... Qa8 24. Nd2 Qxe4 25. Nxe4 Rc7 26. f4 c4 27. bxc4 Rxc4 28. Rxc4 bxc4 29.

Kf2 Kf8 30. Ke2 Nc7 31. Bd2 Nd5 32. Nc3 Nb4 33. Ke3 Nc2+ 34. Ke4 Bb4 35. g4 Ke8

36. Kd5 Na3 37. Kd4 g6 38. Ne4 Nc2+ 39. Kxc4 Bxd2 40. Nxd2 Ne3+ 41. Kd4 Ng2 42.

Ke4 Ne1 43. Nb3 Nc2 44. a4 {

1-0 Bellin,R (2400)-Botterill,G (2365)/Swansea 1987/TD}) 18... Qc8 19. Nd2 (19.

Qe4 c5 20. h4 Ra7 21. Ng5 Nxg5 22. hxg5 Rd7 23. Rde1 Rfd8 24. e6 fxe6 25. Qxe6+

Kh8 26. Bf4 Bd6 27. Be3 Re7 28. Qxc8 Rxc8 29. Rd1 Be5 30. Bxc5 Rf7 31. b3 Rf5

32. Be3 Bf4 33. Bxf4 Rxf4 34. Rd6 a5 35. Rfd1 Kg8 36. g3 Rf5 37. f4 Rc2 38.

R1d2 Rfc5 39. Kg2 Kf7 40. g4 a4 41. bxa4 bxa4 42. Kg3 R5c3+ 43. Kh4 Rxd2 44.

Rxd2 Rf3 45. f5 Kf8 46. Rd8+ Kf7 47. Rh8 Rf2 48. a3 Rh2+ 49. Kg3 Ra2 50. Rxh7

Rxa3+ 51. Kf4 Ra1 52. g6+ Kg8 53. Kg5 a3 54. Rh3 a2 55. Rh2 Kf8 56. Re2 {

1-0 Slaby,J (2401)-Naranjo Moreno,A (2169)/Campillos 2005/CBM 104 ext}) 19...

Rd8 20. f4 c5 21. Qh3 Rd3 22. Ne4 Rxd1 23. Rxd1 Qc7 24. Nc3 Rd8 25. Nd5 Qb7 26.

Qf3 Kh8 27. Nxe7 Qxe7 28. Rxd8+ Qxd8 29. f5 Nd4 30. Qe4 Kg8 31. Kf1 g6 32. g4

Qc8 33. e6 gxf5 34. gxf5 Qc6 35. Qg4+ Kf8 36. Bh6+ Ke7 37. f6+ Kxf6 38. Bg5+

Ke5 39. exf7 Qh1+ 40. Kf2 Qxh2+ 41. Qg2 Qxg2+ 42. Kxg2 Ne6 43. Be7 c4 44. Kg3

a5 45. a3 Kf5 1/2-1/2