What are the best books on the Queen's Gambit Declined?

What are the best books or other resources on the Queen's Gambit Declined?

Looking at this from black's perspective mostly but any resources would help!

chessable would be a great recourse

The best book on the Queen's Gambit Declined is not a book, it is a data base with grandmaster games. Study the games.

I'll definitely try that thanks!

Hmmm interesting take, will try to mainly do that. Thanks!

Check out "Queen's Gambit Declined" by GM Matthew Sadler (from Everyman Chess).

Sadler explains the ideas behind all the main variations, and things to keep in mind, in a really simple manner, move by move. I picked up a lot of nice ideas from it.

Thanks! I'll try it out

I second that motion. Sadler's book is not an attempt at a comprehensive study of the QGD, but it does an outstanding job of explaining the variations that it covers. 

Update on this thread: Roman Dzindzichashvili's video series should be praised as one of the best things ever in instructional chess. That man's an excellent teacher of openings & ideas, as well as being a brilliant player.

Will continue reading books by both Schandorff & by Sadler