Our Solution
Created module that allows users to add links (internal or external) to nodes that can provide further information about the current node. The important thing is that users need not to have edit permissions for the node. You can allow users with non-edit permissions to add/attach new links to nodes.
This module can provide a References/See also/Bibliography kind of links for nodes. You can control which content types you want the urls to be attached to.
Reference links:
http://drupal.org/project/reference_links
