diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
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+# Contributing to Python
+
+:+1::tada: First of off, thanks very much for taking the time to contribute! :tada::+1:
+
+The following is a set of guidelines for contributing to PythonRobotics. 
+
+These are mostly guidelines, not rules. 
+
+Use your best judgment, and feel free to propose changes to this document in a pull request.
+
+# Before contributing
+
+## Taking a look at the paper.
+
+Please check this paper to understand the philosophy of this project.
+
+- [\[1808\.10703\] PythonRobotics: a Python code collection of robotics algorithms](https://arxiv.org/abs/1808.10703) ([BibTeX](https://github.com/AtsushiSakai/PythonRoboticsPaper/blob/master/python_robotics.bib))
+
+## Check your Python version.
+
+We only accept a PR for Python 3.6.x or higher.
+
+We will not accept a PR for Python 2.x.
diff --git a/README.md b/README.md
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@@ -4,6 +4,7 @@
 [![Build Status](https://travis-ci.org/AtsushiSakai/PythonRobotics.svg?branch=master)](https://travis-ci.org/AtsushiSakai/PythonRobotics)
 [![Documentation Status](https://readthedocs.org/projects/pythonrobotics/badge/?version=latest)](https://pythonrobotics.readthedocs.io/en/latest/?badge=latest)
 [![Build status](https://ci.appveyor.com/api/projects/status/sb279kxuv1be391g?svg=true)](https://ci.appveyor.com/project/AtsushiSakai/pythonrobotics)
+[![Coverage Status](https://coveralls.io/repos/github/AtsushiSakai/PythonRobotics/badge.svg?branch=master)](https://coveralls.io/github/AtsushiSakai/PythonRobotics?branch=master)
 [![Say Thanks!](https://img.shields.io/badge/Say%20Thanks-!-1EAEDB.svg)](https://saythanks.io/to/AtsushiSakai)
 
 Python codes for robotics algorithm.