A20 - A29

------------------------------------ A20 ------------------------------------

A20 English opening

1.c2c4 e7e5

   A20 English, Nimzovich variation

   1.c2c4 e7e5 g1f3

      A20 English, Nimzovich, Flohr variation

      1.c2c4 e7e5 g1f3 e5e4

------------------------------------ A21 ------------------------------------

A21 English opening

1.c2c4 e7e5 b1c3

   A21 English, Troeger defence

   1.c2c4 e7e5 b1c3 d7d6 g2g3 c8e6 f1g2 b8c6

   A21 English, Keres variation

   1.c2c4 e7e5 b1c3 d7d6 g2g3 c7c6

   A21 English opening

   1.c2c4 e7e5 b1c3 d7d6 g1f3

      A21 English, Smyslov defence

      1.c2c4 e7e5 b1c3 d7d6 g1f3 c8g4

   A21 English, Kramnik-Shirov counterattack

   1.c2c4 e7e5 b1c3 f8b4

------------------------------------ A22 ------------------------------------

A22 English opening

1.c2c4 e7e5 b1c3 g8f6

   A22 English: Bellon gambit

   1.c2c4 e7e5 b1c3 g8f6 g1f3 e5e4 f3g5 b7b5

   A22 English: Carls' Bremen system

   1.c2c4 e7e5 b1c3 g8f6 g2g3

      A22 English: Bremen, reverse dragon

      1.c2c4 e7e5 b1c3 g8f6 g2g3 d7d5

      A22 English: Bremen, Smyslov system

      1.c2c4 e7e5 b1c3 g8f6 g2g3 f8b4

------------------------------------ A23 ------------------------------------

A23 English: Bremen system, Keres variation

1.c2c4 e7e5 b1c3 g8f6 g2g3 c7c6

------------------------------------ A24 ------------------------------------

A24 English: Bremen system with ...g6

1.c2c4 e7e5 b1c3 g8f6 g2g3 g7g6

------------------------------------ A25 ------------------------------------

A25 English: Sicilian reversed

1.c2c4 e7e5 b1c3 b8c6

   A25 English: closed system

   1.c2c4 e7e5 b1c3 b8c6 g2g3 g7g6 f1g2 f8g7

      A25 English: closed, Taimanov variation

      1.c2c4 e7e5 b1c3 b8c6 g2g3 g7g6 f1g2 f8g7 e2e3 d7d6 g1e2 g8h6

      A25 English: closed, Hort variation

      1.c2c4 e7e5 b1c3 b8c6 g2g3 g7g6 f1g2 f8g7 e2e3 d7d6 g1e2 c8e6

      A25 English: closed, 5.Rb1

      1.c2c4 e7e5 b1c3 b8c6 g2g3 g7g6 f1g2 f8g7 a1b1

         A25 English: closed, 5.Rb1 Taimanov variation

         1.c2c4 e7e5 b1c3 b8c6 g2g3 g7g6 f1g2 f8g7 a1b1 g8h6

      A25 English: closed system (without ...d6)

      1.c2c4 e7e5 b1c3 b8c6 g2g3 g7g6 f1g2 f8g7 d2d3

------------------------------------ A26 ------------------------------------

A26 English: closed system

1.c2c4 e7e5 b1c3 b8c6 g2g3 g7g6 f1g2 f8g7 d2d3 d7d6

   A26 English: Botvinnik system

   1.c2c4 e7e5 b1c3 b8c6 g2g3 g7g6 f1g2 f8g7 d2d3 d7d6 e2e4

------------------------------------ A27 ------------------------------------

A27 English: three knights system

1.c2c4 e7e5 b1c3 b8c6 g1f3

------------------------------------ A28 ------------------------------------

A28 English: four knights system

1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6

   A28 English: Nenarokov variation

   1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 d2d4 e5d4 f3d4 f8b4 c1g5 h7h6 g5h4 b4c3

     b2c3 c6e5

   A28 English: Bradley Beach variation

   1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 d2d4 e5e4

   A28 English: four knights, Nimzovich variation

   1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 e2e4

   A28 English: four knights, Marini variation

   1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 a2a3

   A28 English: four knights, Capablanca variation

   1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 d2d3

   A28 English: four knights, 4.e3

   1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 e2e3

      A28 English: four knights, Stean variation

      1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 e2e3 f8b4 d1c2 e8g8 c3d5 f8e8 c2f5

      A28 English: four knights, Romanishin variation

      1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 e2e3 f8b4 d1c2 b4c3

------------------------------------ A29 ------------------------------------

A29 English: four knights, kingside fianchetto

1.c2c4 e7e5 b1c3 b8c6 g1f3 g8f6 g2g3