Remove duplicate link

free-programming-books.md

@@ -1405,7 +1405,6 @@ See also [TeX](#tex)
 * [Non-Programmer's Tutorial for Python 3](http://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_3) (3.3)
 * [Porting to Python 3: An In-Depth Guide](http://python3porting.com/) (2.6 - 2.x & 3.1 - 3.x)
 * [Practical Programming in Python](https://launchpadlibrarian.net/165489933/PracticalProgrammingPython2014.pdf) - Jeffrey Elkner
-* [Problem Solving with Algorithms and Data Structures](http://interactivepython.org/courselib/static/pythonds/index.html)
 * [Program Arcade Games With Python And Pygame](http://programarcadegames.com/) (3.3)
 * [Python 2.7 quick reference](http://infohost.nmt.edu/tcc/help/pubs/python/web/) - New Mexico Tech (2.7)
 * [Python Bibliotheca](http://openbookproject.net/pybiblio/)