added book link to readme

Author: unpingco

README.md

@@ -3,7 +3,8 @@ IPython notebooks for Python for Signal Processing Book.
 This book is [available as a
 blog](http://python-for-signal-processing.blogspot.com) where you can read the
 formatted notebooks and comment further. The following are the **draft**
-IPython notebooks.
+IPython notebooks. A subset of the blog and the content here is available
+in printed form via [ Springer on Amazon ](http://www.amazon.com/Python-Signal-Processing-Featuring-Notebooks/dp/3319013416).
 
 Notebook Viewer Static Page Views
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