itunes warning – Button doesn’t help

Hello,

The plugin keeps warning me that some booklinks still point to itunes.apple.com. A click on the button to fix this automatically doesn’t work (many clicks don’t either ;-).
I’ve gone through all the books and I can’t find another link to itunes.apple.com, which baffles me. Can you tell me in which database table/field I can find this information, so I can isolate the book I’m missing? (I know my way around databases. ??

Thank you for a beautiful plugin and regards,
Paul