diff --git a/README.rst b/README.rst
index 8ce1385..326c086 100644
--- a/README.rst
+++ b/README.rst
@@ -4,6 +4,9 @@ Olm
 An implementation of the cryptographic ratchet described by
 https://github.com/trevp/axolotl/wiki, written in C++11 and exposed as a C API
 
+The specification of the Olm ratchet can be found in docs/olm.rst or
+https://matrix.org/docs/spec/olm.html
+
 Building
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