Dear Developers, If you: 1) edit the ISBD and OPACISBD system preferences so that they contain the following code: #453| - translated as: |<a href="/cgi-bin/koha/catalogue/ detail.pl?biblionumber={4530}">{453t}</a> {(453d)}| #454| - translation of: |<a href="/cgi-bin/koha/catalogue/ detail.pl?biblionumber={4540}">{454t}</a> {(454d)}| 2) set the visibility of (UNIMARC) fields 453$0 and 454$0 to 'hidden' in the OPAC ...then the generated links will work fine in the Staff client but will be broken in the OPAC (i.e. the URL will not include the biblionumber contained in subfield 0 of fields 453/454). I've tracked this down to ISBDdetail.pl and opac-ISBDdetail.pl calling the GetISBDView subroutine, which (for some reason) excludes subfields that are hidden in the OPAC: https://github.com/Koha-Community/Koha/blob/master/C4/Biblio.pm#L773-L776 https://github.com/Koha-Community/Koha/blob/master/C4/Biblio.pm#L812-L815 What is the reasoning behind this? In other words, why is _OPAC_ subfield visibility taken into account when displaying the OPAC ISBD view (whereas visibility in Staff is not considered)? If anything, it is more likely to have subfield 0 hidden in OPAC, while visible in Staff, so one would expect the opposite logic. Thanks in advance for your time. Kind regards, Andreas Roussos