Hello, I am about to import a catalog from another library software to Koha via a MARC 21 (*.mrc) file. Are there essential MARC fields which must not lack in a single entry so that Koha imports it correctly? Frank -- Koha: 3.18.01.000 OS: Linux hgkkoha 3.2.0-4-amd64 #1 SMP Debian 3.2.63-2+deb7u2 x86_64 GNU/Linux Perl: 5.014002koha 3.18.01.000