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+This is the source code repository for ERFA (Essential Routines for
+Fundamental Astronomy).  ERFA is a C library containing key algorithms for
+astronomy, and is based on the `SOFA library <http://www.iausofa.org/>`_ published by the International
+Astronomical Union (IAU).
+
+ERFA is intended to replicate the functionality of SOFA (aside from possible
+bugfixes in ERFA that have not yet been included in SOFA), but is licensed
+under a three-clause BSD license to enable its compatibility with a wide
+range of open source licenses. Permission for this release has been
+obtained from the SOFA board, and is avilable in the ``LICENSE`` file included
+in this source distribution.
+
+Differences from SOFA
+---------------------
+
+This version of ERFA (v1.3.0) is based on SOFA version "20160503_a", with the
+differences outlined below.
+
+ERFA branding
+^^^^^^^^^^^^^
+
+All references to "SOFA" in the source code have been changed to ERFA, and
+functions have the prefix ``era`` instead of ``iau``.
+
+C macro prefixes
+^^^^^^^^^^^^^^^^
+
+All C macros used in ERFA are the same as their SOFA equivalents, but with an
+``ERFA_`` prefix to prevent namespace collisions.
+
+Bugfixes
+^^^^^^^^
+
+ERFA includes smaller changes that may or may not eventually make it into SOFA,
+addressing localized bugs or similar smaller issues:
+
+* ERFA 1.3.0 and SOFA "20160503_a"
+
+  + There are no differences between ERFA 1.3.0 and SOFA "20160503_a".
+
+* ERFA 1.2.0 and SOFA "20150209_a"
+
+  + Typos have been corrected in the documentation of atco13 and atio13 (see https://github.com/liberfa/erfa/issues/29).
+
+Note that issues identified in ERFA should generally also be reported upstream to SOFA at sofa@ukho.gov.uk.
+
+Building and installing ERFA
+----------------------------
+
+To build and install a released version of ERFA in your OS's standard
+location, simply do::
+
+    ./configure
+    make
+    make install
+
+If you want to run the tests to make sure ERFA built correctly, before
+installing do::
+
+    make check
+
+
+For developers
+^^^^^^^^^^^^^^
+
+If you are using a developer version from github, you will need to first do
+``./bootstrap.sh`` before the above commands. This requires ``autoconf`` and
+``libtool``.
+
+If you wish to build against the ERFA static library without installing, you
+will find it in ``$ERFAROOT/src/.libs/liberfa.a`` after running ``make``.
+
+Creating a single-file version of the source code
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Alternatively, if you wish to bundle the ERFA source code with a separate
+package, you can use the ``source_flattener.py`` script from the
+`erfa-fetch repository`_ to combine
+the ERFA source code into just two files: a ``erfa.c`` source file, and an
+``erfa.h`` include file.  You should run this script like this::
+
+    cd /path/to/erfa-source-code
+    python /path/to/erfa-fetch/source_flattener.py src -n erfa
+
+If possible, however, it is recommended that you provide an option to use any
+copy of the ERFA library that is already installed on the system.
+
+Travis build status
+-------------------
+.. image:: https://travis-ci.org/liberfa/erfa.png
+    :target: https://travis-ci.org/liberfa/erfa
+
+.. _erfa-fetch repository: https://github.com/liberfa/erfa-fetch