Introduction to Queen's Gambit:
Wikipedia about Queen's Gambit
Queen's Gambit Accepted
Wikipedia
The Queen's Gambit Accepted/Isolated Queen's Pawn (Exeter Chess Club)
Queen's Gambit Declined
Queen's Gambit Declined (Chess Corner)
Lectures by Steve Stoyko
Topalov - Anand, 2010 (Game 12)
Vyzmanavin - Ruban, 1989
Tarrasch (D40)
Queen's Gambit Semi-Slav
Wikipedia
David Vigorito: Play the Semi-Slav
Adventures in the Semi-Slav
Koneru - Danielian, 2013
Queen's Gambit Slav
Wikipedia
Alekhine Variation 4...dxc4 5.e3
Wikipedia about Queen's Gambit
Queen's Gambit Accepted
Wikipedia
The Queen's Gambit Accepted/Isolated Queen's Pawn (Exeter Chess Club)
Queen's Gambit Declined
Queen's Gambit Declined (Chess Corner)
Lectures by Steve Stoyko
Topalov - Anand, 2010 (Game 12)
Vyzmanavin - Ruban, 1989
Tarrasch (D40)
Queen's Gambit Semi-Slav
Wikipedia
David Vigorito: Play the Semi-Slav
Adventures in the Semi-Slav
Koneru - Danielian, 2013
Queen's Gambit Slav
Wikipedia
Alekhine Variation 4...dxc4 5.e3