Nimzo-Indian, Sämisch Variation 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. a3 Bxc3+ 5. bxc3 c5
In each game under Location you see masterchessopen.com but it's not a valid website, so please don't use it. Claus Gamborg, Jan. 2023