diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 3b62d30..a1e7808 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -10,6 +10,10 @@ In general, I follow strict pep8 and pyflakes.  All code must pass these tests.
 
 All code needs to support Python 2.4-3.4.
 
+# Permitted Python Modules
+
+Only modules included in the standard library are permitted for use in this application.  This application should not be dependent on any 3rd party modules that would need to be installed external to just Python itself.
+
 # Testing
 
 Currently there are no unit tests, but they are planned.