| $(url_refs) - References to URLs
                          URLs of defined <out> sections and <media> items can be inserted
                          into the current content using this reference format.
                          
                         
                          
                            $(name)
                           
                          Note that all URL references are written relatively; so a file created in the
                          foo/bar/baz subdirectory which contains a URL reference to
                          blah/argh.html will be rewritten to refer to ../../../blah/argh.html.
                          
                         
                          Again, if you're not sure a URL exists, a default value can be supplied,
                          using this format:
                          
                         
                          
                            $(name?defaultvalue)
                           
                          
                         |