J. Paul Morrison, "Flow-Based Programming", van Nostrand Reinhold, 1994, ISBN: 0-442-01771-5 .
http://www.jpaulmorrison.com/fbp/
http://www.amazon.com/exec/obidos/ISBN%3D0442017715
See FlowBasedProgramming.
This book is now out of print, and all new copies have been sold. There are (currently) some second-hand copies listed on Amazon.com. I am currently thinking about making a new version available via BookSurge, but this will have a different ISBN code. Feedback would be welcome!