8. The non-transitory computer-readable storage medium of claim 7 , wherein inserting the first user's notes into the second user's existing notes comprises inserting a reference or a pointer, within the document, to the first user's notes in the second user's existing notes.
9. The non-transitory computer-readable storage medium of claim 8 , wherein notifying the second user of the availability of the shared notes comprises sending a notification message to the second user.