<?xml version="1.0" encoding="utf-8"?><mads xmlns="http://www.loc.gov/mads/" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mads/
mads.xsd"><authority><topic authority="http://AATesaurus.cultura.gencat.cat/aat/getty_en">NBN</topic></authority><related type="broader"><topic>identification numbers</topic></related><variant type="other"><topic>National Bibliography Number</topic></variant><variant type="other"><topic>National Bibliography Numbers</topic></variant> <note xml:lang="en"><![CDATA[ Persistent and unique identifiers assigned by national libraries, used to identify resource descriptions. There is no global standard for the contents of NBNs, but each nation may have a country-specific format. ]]></note></mads>