[%c_effect c5;square;c5;type;GreatFind;persistent;true] There are two possible doubles for the d2-knight: one on c4 and one on d6.
1. d2d4  1... d7d5  2. c2c4  2... c7c6  3. g1f3  3... g8f6  4. b1c3  4... e7e6  5. c1g5  5... b8d7  6. e2e3  6... d8a5 The Cambridge-Springs Variation is a more solid choice for Black than the complications of the Botvinnik System with 6...dxc4. For those interested in classic games with this system, I suggest studying games 7, 9 and 11 of the match Capablanca vs. Alekhine. 7. c4d5  7... f6d5  8. a1c1  8... h7h6 It's usually difficult to know if the ...h6 move is useful; I have doubts about this in several defenses. Many players prefer to take on c3 right away. Others choose 8...Bb4. 9. g5h4  9... d5c3  10. b2c3  10... f8a3  11. c1c2  11... b7b6 [%c_effect b6;square;b6;type;GreatFind;persistent;true] This plan is essential for Black: playing the bishop to a6 and simplifying the position a bit. 12. f3d2 [%c_effect d2;square;d2;type;Interesting;persistent;true] A relatively rare move, but one that has been tried in some correspondence games. 12... c8a6  13. c3c4 The most natural move. 13... e8g8  14. f1d3  14... c6c5  15. e1g1  15... c5d4  16. e3d4  16... f8e8  17. d1e2  17... a8c8 [%c_effect c8;square;c8;type;Inaccuracy;persistent;true] This move is inaccurate and leads to problems. The correct path is shown in one of the correspondence games.