I have been adding my sources with a copy of the text of the document in the section Personal Memories. For example:
Hi Theresa,
I assume you've seen this: http://www.wikitree.com/wiki/Sources
If you want to include details on the sources, I'd still try to find a space for it in the sources section.
The Personal Memories section really isn't right, since those are supposed to be first-hand memories.
Chris