(D21) Ericson
1. d4 d5 2. c4 dxc4 3. Nf3 b5
(D21) Alekhine
1. d4 d5 2. c4 dxc4 3. Nf3 a6
(D21) Alekhine (Borisenko-Furman)
1. d4 d5 2. c4 dxc4 3. Nf3 a6 4.e4