<!-- http://isbn.example.org/1906833214 which we need to search -->
<!-- by our usual substring match. Or they can be links to Identivfiers -->
<!-- which will have a proper identifierValue on which we can do -->
<!-- http://isbn.example.org/1906833214 which we need to search -->
<!-- by our usual substring match. Or they can be links to Identivfiers -->
<!-- which will have a proper identifierValue on which we can do -->