spec: write section: reference implementation
diff --git a/docs/imsi-pseudo-spec.adoc b/docs/imsi-pseudo-spec.adoc
index a8bdf80..eb5006d 100644
--- a/docs/imsi-pseudo-spec.adoc
+++ b/docs/imsi-pseudo-spec.adoc
@@ -190,6 +190,7 @@
// FIXME: do we need to enforce the LU now, with an arbitrary CM Service
// Request, or would this only be necessary for Osmocom? (OS#4404)
+[[process-update-location-hlr]]
=== Process Update_Location_HLR
All IMSI Pseudonymization related changes to Process Update_Location_HLR
@@ -346,6 +347,17 @@
[[reference-src]]
== Reference Implementation with Source Code
+A reference implementation for the SIM applet (<<sim-app>>) is available in
+source code under the Apache-2.0 license at:
+
+https://osmocom.org/projects/imsi-pseudo
+
+The HLR modifications described in <<hlr-imsi-pseudo-storage>> and
+<<process-update-location-hlr>> were implemented for reference in OsmoHLR from
+the Osmocom project, licensed under AGPL-3.0. Information about the source code
+and related branches for IMSI pseudonymization can be found at the above URL as
+well.
+
== Recommendations for Real-World Implementations
=== ATT = 0
=== End to End Encryption of SMS