README.md

@@ -4,6 +4,7 @@ This repository contains OpenAPIs descriptions for the interfaces specified in E
 
 ## Online resources
 
+* [Specification document](https://www.etsi.org/deliver/etsi_gs/MEC/001_099/013/01.01.01_60/gs_mec013v010101p.pdf)
 * [Navigate the API in the browser](https://forge.etsi.org/rep/gitweb.cgi/MEC.GS_013.git/blob/HEAD:/LocationAPI.yaml#swagger).
 * [Edit the API online](https://forge.etsi.org/swagger/editor/?url=https://forge.etsi.org/rep/gitweb.cgi/MEC.GS_013.git/blob_plain/HEAD:/LocationAPI.yaml).