Where can I find a good introduction or documentation on Objective-C blocks?

Question

I am trying to use blocks in Objective-C. I have worked through this tutorial , but I would like to know more about the blocks.

Where should I look for the best documentation or tutorials on Objective-C blocks and their use?

Answer 1

Gather the answers from the comments (and turn this community community wiki for justice), so we have the answer to this question:

Apple white papers

http://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/Blocks/

Mike Ash

http://mikeash.com/pyblog/friday-qa-2009-08-14-practical-blocks.html

Cocoa

http://cocoawithlove.com/2009/10/how-blocks-are-implemented-and.html