github link and acknowledgments section

preface.asciidoc

@@ -19,6 +19,10 @@ _The best way to get the right answer on the Internet is not to ask a question,
 
 I hope you can help me find and publish the "right answer" by the time this book is ready to print.
 
+The early-realease source code is published on Github: https://github.com/aantonop/bitcoinbook
+
+File an "Issue", or fork, modify and create a "Pull Request" with your changes.
+
 === Why Are There Bugs On The Cover?
 
 The Leafcutter Ant is a species that exhibits highly complex behavior in a colony super-organism, but each individual ant operates on a set of simple rules driven by social interaction and the exchange of chemical scents (pheromones). Per Wikipedia: "Next to humans, leafcutter ants form the largest and most complex animal societies on Earth." Leafcutter ants don't actually eat leaves, but rather use them to farm a fungus, which is the central food source for the colony. Get that? These ants are farming! 
@@ -181,6 +185,27 @@ transaction::
 wallet::
 ((("wallet"))) 
 	Software that holds all your addresses. Use it to send bitcoin and manage your keys.
+    
+++++
+<?hard-pagebreak?>
+++++
+
+== Acknowledgments
+
+=== Early Release Draft (Github Contributions)
+
+Many contributors offered comments, corrections and additions to the early-release draft on Github. Thank you all for your contributions to this book. Notable contributions included:
+
+Minh T. Nguyen - enderminh: Github contribution editor
+
+Eric Winchell - winchell
+Sergej Kotliar - ziggamon
+Erik Wahlström - erikwam 
+ishotjr
+Mihail Russu - MihailRussu
+
+
+