411 REFERENCE · Wikibooks
Chess Opening Theory/1. d4/1...d5/2. c4/2...e6/3. Nc3/3...Nf6/4. Bg5/4...Be7/5. e3
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Queen's Gambit Declined D54-D69 Orthodox variation
5. e3
With the dark-squared bishop developed, White can safely create a dark-squared pawn-chain.
Theory table
5...O-O 5...h6 5...Nbd7
References
See also