diff --git a/README.md b/README.md
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@@ -7,3 +7,5 @@ python-opencivicdata-django
 [![Download Format](https://pypip.in/format/opencivicdata-django/badge.png)](https://pypi.python.org/pypi/opencivicdata-django/)
 
 This package is part of the opencivicdata namespace package containing the utilities for using Open Civic Data data models in Django.
+
+Its Organization, Person, Membership, Post, and VoteEvent models and related models are based on the [Popolo specification](http://popoloproject.com/).