In Koha 19.05 manual in chapter https://koha-community.org/manual/19.05/en/html/searching.html#indexing-and-searching-description there is a non-working link: http://www.indexdata.dk/zebra/doc/zebra.pdf - the correct link is probably https://software.indexdata.com/zebra/doc/idzebra.pdf (NB: At the moment Bugzilla does not know Koha 19.05 so I opened this bug for Koha 18.11 where in fact the link is also wrong)
Created a merge request on gitlab: https://gitlab.com/koha-community/koha-manual/merge_requests/237 Not sure which status to use here, setting resoled as things have moved to gitlab now.