Si,
I have a field I create in any tiddler relating to discussions we have here in GG. In edit mode I just create the "discussion" field and past the link to the GG item.
I have a small viewTemplate that displays the link as "discussion" at the bottom of any tiddler found like that.
In the near future I intend provide an opportunity to drop one or more links on a tiddler and create one or more fields with the suffix "-link", then the caption for such a link can be anything before the "-link" in 5.2.0 and its new field naming freedom.
Your stylesheet example however may best be handled using Sorens suggested comments areas. Keep in mind you can build a way to find and display such comments from any tiddler especially if you make a de facto standard;
eg
<!-- source name url notes -->
Then you can search for tiddlers with lines beginning "<!-- source" use the name with the url and follow this with the notes.
To simplify the search you could add a field called contains-sources=yes
You could even display this At the bottom of each tiddler containing such comments.
Regards
Tones