"Who can recommend good books/articles on negotiation?"
The best book on negotiation, bar none, is "Bargaining for Advantage : Negotiation Strategies for Reasonable People" By Richard Shell.
http://www.amazon.com/Bargaining-Advantage-Negotiation-Strat...
(looks like it is out of print, but used copies seem cheap enough)
To the OP: Seriously, if there is one book you are going to read on negotiation, make it this one. The things you learn using this book can be put to use.
There's a new edition out:
http://www.amazon.com/Bargaining-Advantage-Negotiation-Strat...