Stefan and "Conquistador":
Yes indeed, the move 3..Nc6 has several possible refutations but always from
4.Qh5+ , not 4.d4 ( John Nunn, "Secret of practical chess" ), so if not, 4..Qe7 or 4..Qf6 can be still allowed. "Conquistador", alternatives you show are clear, and other ways I know as Black are also invalid.
I still believe after 3..Qf6
key is 4.d4 d6 5.Nc4 fxe4 etc.
The other main line from 4.Nc4 fxe4 5.Nc3, also allows besides 5..Qf7 6.Ne1
d5!? ( which it must be analyzed in depth, so although Black sacrifices a pawn, his development is up, and practice has shown it is very difficult for White to win ), the former move
5..Qg6.
The move was already quoted in
http://www.chesspub.com/cgi-bin/yabb2/YaBB.pl?num=1239692688 . I wrote something more in my own blog (
http://amm-ajedrezando.blogspot.com/2009/11/gambito-leton-analisis-1.html in Spanish ), but now I will translate it here:
After 5..Qg6, as I have quoted, Black Queen is a bit exposed and White often proceed with its relentless with d3 and after the exchange of pawns recapturing with the Bishop. Although it was the initial line, was gradually abandoned ( in favour of 5..Qf7 ) until recently amateur David Zimbeck in his web
http://www.zimbeckchess.com/chess_site_006.htm may have recovered somewhat its value.
Zimbeck maintains after well-known and natural White moves 6.d3 Bb4 7.Bd2, Black must now play directly
7..Nf6 ( instead of 7..Bxc3 8.Bxc3 Nf6 ) so even losing a whole pawn, allows second player remain in the game:
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8.dxe4 0-0!? 9.f3 d5 10.Nxd5 Nxd5 11.exd5 Bc5 of
Melchor-Valverde, cr. LADAC thema, e-mail, 2006/07, ( 1/2-1/2, 47 ) led to a difficult ending where White never seemed with possibility of win. My position was always better, but the Black position was sound.
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8.dxe4 Bxc3 9.Bxc3 Nxe4 10.Bd3 0-0 11.0-0 Nxc3 12.bxc3 is known from first thematic tournaments of 1970's ( also Hagen Tiemann in the second 1989 edition of his book of Latvian, page 22 ). I have 25 games, and it has been tested 12..Qg5; 12..Qh6; and 12..Qf6.I believe this last move,
12..Qf6 ( 12 games ), is pehaps best one. I cannot deny after 13.Qh5 g6 14.Qa5
Qd8!? ( I don't like 14..Nc6 of Tiemann, or 14..Na6, or 14..c6 of several games ) and with the help of ...
Rybka3, the position, although "nasty" and poorly developed for Black, is perfectly playable, … at least in postal chess ( I myself have tested dozens of lines ). Truly it is sad Black recourse to these lines, but what else? if we have so tight margin !.
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8.Nxe4 Bxd2+ 9.Qxd2 ( American player also gives 9.Nexd2 0-0 10.Ne1 d5 and both 11.d4 or 11.Nf3, then 11..Ng4! )
9..d5 ( 9..0-0 is inferior ). This position was known from a game
Ginzburg-Perez Pietronave, Argentina, 1995 which it followed according to the recommendation of the "engines"
10.Nxf6+ Qxf6 11.Qe3+ Be6 12.Ne5 0-0 13.Be2 ( 13. d4 Nc6 Zimbeck, and now could be continue 14.Bd3 Bf5 15.0-0 Bxd3 16.cxd3 Qd6 without problems )
13..Nd7 14.d4 and now diverting from the game, Black should play
14..Nxe5 15.dxe5 Qg6 ( or even
14..Qf4 ) which it takes to a comfortable position, and also recovering the pawn.
It is already noteworthy Zimbeck show next beautiful line:
10.Ne5 Nxe4! 11.Nxd2 Nxg6 12.Nxf1 Nxh8 etc. subject of debate linked above and although engines spend a few time in viewing, just give reason Black side.
Alejandro Melchor
PS. If somebody wants my "Godzilla" Base ( 15000 games, many of them with notes ) I could send him. You can write me to
amelchor@eresmas.net.
Hmm,... I think we should write another book

so i'ts impossible to talk all time on Latvian !?