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ECO A21

ECO A00–A99 — Flank openings: 1.c4, 1.Nf3, 1.f4 and other first moves, plus early Indian and Benoni systems.

5 named opening lines are classified under ECO code A21.

English Opening: King's English Variation, Keres Defense — 1.c4 e5 2.Nc3 d6 3.g3 c6
English Opening: King's English Variation, Kramnik-Shirov Counterattack — 1.c4 e5 2.Nc3 Bb4
English Opening: King's English Variation, Reversed Sicilian — 1.c4 e5 2.Nc3
English Opening: King's English Variation, Smyslov Defense — 1.c4 e5 2.Nc3 d6 3.Nf3 Bg4
English Opening: King's English Variation, Troger Defense — 1.c4 e5 2.Nc3 Nc6 3.g3 d6 4.Bg2 Be6