I enabled 7xx field linking and we're having some trouble.

The example record is here: http://gr171.grrl.lib.mn.us/Record/650198 (please ignore the hot pink, we're working on a color matching issue).

If you click the "Continued by" link you get "No Results!" I believe it's because our ISBN field contains additional notes. Shouldn't the Continued by field use a stripped-down form of the ISBN field? How can I fix it?