doc: reference vault repository

README.md

@@ -61,7 +61,7 @@ Tests have been implemented using the Molecule framework. The details on using t
 
 ## Variables
 
-Many variables have been "hidden" in encrypted Ansible Vaults. However, in order to better understand the data within the vaults, you can find `\*.vault.example` files below the `vars/` directory.
+Many variables have been "hidden" in encrypted Ansible Vaults. For security reasons, these Vaults are maintained in a separate private internal repository of SLUB's Git. However, in order to better understand the data within the vaults, you can find `\*.vault.example` files below the `vars/` directory.
 
 ## git configuration