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<h1>Authorised values management</h1>
<p>Koha allows you to restrict the values that catalogers can place in some MARC subfields to certain pre-defined "authorised" values. These authorised values are defined here.</p>

<p>For example, if your Koha installation is used by several libraries, and you use MARC21, you might want to restrict the 850a MARC subfield to the instition codes for just those libraries. In that case, you could define a new authorised values category (perhaps called "INST") and enter the institution codes as the authorised values for that category. Once the 850a subfield is linked to the INST authorised values category in your MARC tag structure, catalogers must choose a value from the list you define here, and may not type in any other value.</p>
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<li>HINT : if a subfield is non mandatory, Koha automatically adds an empty value to the authorised value list, that is selected by default. If the subfield is mandatory, no empty value is added (and you should NOT add it in the list, as it's an illegal value !)</li>
<li>HINT2 : in the MARC editor, the list is ordered by Text, NOT by value. So you can define a default value by putting a space before the value you want to see first. For example, if your list is related to language, you can set "ENG" as authorised value and " English" as text. The space will order "ENG" as first default value, and the space won't be shown (because HTML automatically discard useless spaces). Super hint : you can put a value 1st with N spaces, then another one 2nd with N-1 space,..., a value in Nth position with 1 space. Don't abuse of this feature, it's easier to find a value in an alphabetical order. It should be used only to have a default value</li>
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<p>Koha automatically sets up authorised value categories for your item types and branch codes, and you can link these authorised values to MARC subfields when you set up your MARC tag structure.</p>
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