Update main README.md

README.md

 # QKD Control Interface for SDN
 
-YANG model for ETSI GS QKD 015, specification of management interfaces between 
-SDN-enabled QKD node and SDN controller.
+YANG models for 
+[ETSI GS QKD 015 V2.1.1 (2022-04)](https://www.etsi.org/deliver/etsi_gs/QKD/001_099/015/02.01.01_60/gs_QKD015v020101p.pdf) 
+"Quantum Key Distribution (QKD); Control Interface for Software Defined Networks", which specifies management interfaces between SDN-enabled QKD node and SDN controller, developed by 
+[ETSI ISG QKD](https://www.etsi.org/committee/qkd)
+
+**An update to this Group Specification is under development in work item [RGS/QKD-015ed3_ContIntSDN](https://portal.etsi.org/webapp/workprogram/Report_WorkItem.asp?WKI_ID=67986).**
+
+**IMPORTANT: Draft updates to the YANG models are being developed in branch [edition3](https://forge.etsi.org/rep/qkd/gs015-ctrl-int-sdn/-/tree/edition3) of this repository and these revisions are subject to change**
 
 Note: The default branch in this repository has been renamed `main` as per QKD(23)033d002.
 
+## Related ISG QKD Repositories
+
+- [YANG models](https://forge.etsi.org/rep/qkd/gs018-orch-int-sdn) for
+  ETSI GS QKD 018 "Quantum Key Distribution (QKD); QKD Orchestration Interface for SDN"
+- [Draft YANG models](https://forge.etsi.org/rep/qkd/gs021-orch-interop-sdn) for
+  draft ETSI GS QKD 021 "Quantum Key Distribution (QKD); Orchestration Interface of Software Defined Networks for Interoperable key management system"
+
 ## Contact
 
 For inquiries, contact `isgsupport` at `etsi` dot `org`.