sympy/sympy — pull request #1685 by nthorne (2012-12-04 12:46:46+00:00)
Title: Fixed dead links in documents

Dead links removed from documentation as per https://code.google.com/p/sympy/issues/detail?id=3520. I left a few links that were temporary unavailable, one that times out, and two that actually resolved just fine when opening them in a browser.