Update README.md

Author: bt3

README.md

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 #  Algorithms & Data Structures in Python
 
-An introduction to Algorithms & Data Structures in Python, including an ["e-book" I wrote](http://mariwahl.us/docs/algorithms_in_python.pdf).
+An introduction to Algorithms & Data Structures in Python, including an ["e-book" I wrote](https://github.com/bt3gl/Python-and-Algorithms-and-Data-Structures/blob/master/book/book_second_edition.pdf).
 
 ![](http://i.imgur.com/MJZjABD.png)