The main variations below are in order of popularity. 3.Nf3 The main lines of the QGA begin with this move. White delays measures to regain the pawn for the moment and prevents Black from striking at the centre with ...e5. The recovery of the pawn will usually be done through 4.e3 and 5.Bxc4. Black's most common rejoinder is 3...Nf6, though the variation 3...a6 was introduced by Alexander Alekhine and bears his name. The main line of the Queen's Gambit Accepted continues with: 3...Nf6 4.e3 4.Qa4+ leads to the Mannheim Variation, so named after its adoption in one of the cities where the World Chess Championship 1934 was played, even though the move was previously known. Black usually gains easy equality after 4...Nc6, so the line is fairly rare. Grandmasters Michał Krasenkow and Ulf Andersson have played the line several times. 4.Nc3 leads to the Two Knights Variation, which is a true gambit line since White can no longer expect to regain the c4-pawn after 4...a6 5.e4 b5. White's compensation in the form of a strong centre leads to immensely complicated play. Black does not need to enter this line, and 4...Nc6, 4...e6, and 4...c6 tend to transpose to the Chigorin Defense, QGD Vienna Variation, and Slav Defense respectively. 4...e6 An alternative is 4...Bg4 (the Janowski–Larsen Variation) 5.Bxc4 e6, usually leading to a solid position, though the game can become sharp if White immediately attempts to exploit the weakness of Black's queenside in the line 6.Qb3 Bxf3 7.gxf3 Nd7 as Black gains great piece activity and spoils White's kingside pawns in return for sacrificing a pawn. 5.Bxc4 c5 6. 0-0 A major alternative to castling is 6.Qe2, called the Furman Variation after Semion Furman. The idea behind 6.Qe2 is to support the advance of the e-pawn. 6...a6 6...cxd4 brings about an isolated queen's pawn structure, and has been called the Steinitz Variation, after Wilhelm Steinitz. This line became well known after his match with Zukertort in 1886, but theory has generally held White's activity in high regard. The early clarification of the central tension gives White too free a hand and the line is rarely seen in modern practice. Black has played to challenge the d4-pawn, and prepare ...b5 which wins time by harassing the bishop on c4. In the meantime, White has safeguarded his king and regained the pawn. At this point, there are several options available for White, who