This will enable more accurate linking. NORMARC: http://git.koha-community.org/gitweb/?p=koha.git;a=blob;f=koha-tmpl/opac-tmpl/prog/en/xslt/NORMARCslim2OPACDetail.xsl;h=3a774171320bcac3bd449feb03490f907330fe85;hb=HEAD#l418 MARC21: http://git.koha-community.org/gitweb/?p=koha.git;a=blob;f=koha-tmpl/opac-tmpl/prog/en/xslt/MARC21slim2OPACDetail.xsl;h=f507e11fcd1a160a193d104f81b96ff902d87f73;hb=HEAD#l744
See bug 18984.