diff -up networkx-networkx-1.11/doc/source/conf.py.sphinx networkx-networkx-1.11/doc/source/conf.py
--- networkx-networkx-1.11/doc/source/conf.py.sphinx	2016-01-30 10:25:44.000000000 -0700
+++ networkx-networkx-1.11/doc/source/conf.py	2016-12-23 09:54:55.280925006 -0700
@@ -74,7 +74,6 @@ extensions = [
     'sphinx.ext.intersphinx',
     'sphinx.ext.mathjax',
     'sphinx.ext.napoleon',
-    'sphinx.ext.pngmath',
     'sphinx.ext.todo',
     'sphinx.ext.viewcode',
     #'sphinxcontrib.bibtex',