For case citations, texts and other lex mercatoria material on good faith and standards of reasonableness and cooperation:
http://tldb.uni-koeln.de/TLDB.html
Click TLDB's "List of Lex Mercatoria Principles".
No. I.1 - Good faith and fair dealing in international trade
"The parties must act in accordance with the standard of good faith and fair dealing in international trade."
No. I.2 - Standard of reasonableness
"The parties always have to act according to what is reasonable in view of the particular nature of their transaction and the circumstances involved, in particular the economic interests and expectations of the parties."
Scroll also to Chapter IV: Contract, Section 5: Contractual obligations
No. IV.5.8 - Duty to notify
"Each party is under a good faith obligation to notify the other party of any problems that occur in the performance of the contract and to cooperate with the other party when such cooperation can reasonably be expected for the performance of that party's obligations."
The TLDB database provides annotations to these texts. The TLDB annotations address Doctrine, Awards, Principles/Model Laws, Conventions, National Legislation, Terms/Rules.
Pace Law School
Institute of International Commercial Law - Last updated January 28, 2003