diff --git a/l18n b/l18n
index 8d83978..808895c 160000
--- a/l18n
+++ b/l18n
@@ -1 +1 @@
-Subproject commit 8d83978b4f1159445f16ed9bb15b791ea9a4724a
+Subproject commit 808895ce187b34de591bbf7f4c1d9039a480e615
diff --git a/src/enums/MDInstitutionExternalIdRepository.php b/src/enums/MDInstitutionExternalIdRepository.php
new file mode 100644
index 0000000..c00b442
--- /dev/null
+++ b/src/enums/MDInstitutionExternalIdRepository.php
@@ -0,0 +1,132 @@
+<?PHP
+/**
+ * Represents a possible repository, in which an institution is listed with an ID.
+ * The ISIL is not covered in this list.
+ *
+ * @author Joshua Ramon Enslin <joshua@museum-digital.de>
+ */
+declare(strict_types = 1);
+
+/**
+ * Represents a possible status for to-dos.
+ */
+enum MDInstitutionExternalIdRepository implements MDValueEnumInterface, JsonSerializable {
+
+    case hu_ksh; // https://en.wikipedia.org/wiki/Hungarian_Central_Statistical_Office
+
+    const VALIDATION_PATTERN_HTML = [
+        'hu_ksh' => '[0-9]{8}-[0-9]{4}-[0-9]{3}-[0-9]{2}',
+    ];
+
+    const VALIDATION_PATTERN_PHP = [
+        'hu_ksh' => '[0-9]{8}-[0-9]{4}-[0-9]{3}-[0-9]{2}',
+    ];
+
+    /**
+     * Returns a value of this type based on a string.
+     *
+     * @param string $input Input to get a value from.
+     *
+     * @return MDInstitutionExternalIdRepository
+     */
+    public static function fromString(string $input):MDInstitutionExternalIdRepository {
+
+        return match($input) {
+            'hu_ksh' => self::hu_ksh,
+            default => throw new MDpageParameterNotFromListException("Unknown external repository"),
+        };
+
+    }
+
+    /**
+     * Lists all available names.
+     *
+     * @return array<string>
+     */
+    public static function caseNames():array {
+
+        $output = [];
+
+        $cases = self::cases();
+        foreach ($cases as $case) {
+            $output[] = $case->name;
+        }
+
+        return $output;
+
+    }
+
+    /**
+     * Gets an unsorted list of the entries in a translated version.
+     *
+     * @param MDTlLoader $tlLoader Translation loader.
+     *
+     * @return array<string, string>
+     */
+    public static function getUnsortedList(MDTlLoader $tlLoader):array {
+        return MDValueSet::getTlUnsortedList($tlLoader, self::caseNames(), "institution_external_id_repositories", "institution_external_id_repositories");
+
+    }
+
+    /**
+     * Gets a sorted list of the entries in a translated version.
+     *
+     * @param MDTlLoader $tlLoader Translation loader.
+     *
+     * @return array<string, string>
+     */
+    public static function getSortedList(MDTlLoader $tlLoader):array {
+        return MDValueSet::getTlSortedList($tlLoader, self::caseNames(), "institution_external_id_repositories", "institution_external_id_repositories");
+
+    }
+
+    /**
+     * Returns the name of the current value in translation.
+     *
+     * @param MDTlLoader $tlLoader Translation loader.
+     *
+     * @return string
+     */
+    public function getTledName(MDTlLoader $tlLoader):string {
+
+        return $tlLoader->tl("institution_external_id_repositories", "institution_external_id_repositories", $this->name);
+
+    }
+
+    /**
+     * Returns the HTML pattern.
+     *
+     * @param MDTlLoader $tlLoader Translation loader.
+     *
+     * @return string
+     */
+    public function getValidationPatternHtml():string {
+
+        return self::VALIDATION_PATTERN_HTML[$this->name];
+
+    }
+
+    /**
+     * Returns the PHP pattern.
+     *
+     * @param MDTlLoader $tlLoader Translation loader.
+     *
+     * @return string
+     */
+    public function getValidationPatternPhp():string {
+
+        return self::VALIDATION_PATTERN_PHP[$this->name];
+
+    }
+
+    /**
+     * Provides the option to serialize as a string during json_encode().
+     *
+     * @return string
+     */
+    public function jsonSerialize():string {
+
+        return $this->name;
+
+    }
+}