diff --git a/src/enums/MDNodaRepository.php b/src/enums/MDNodaRepository.php
index 5f84ebc..677bb3b 100644
--- a/src/enums/MDNodaRepository.php
+++ b/src/enums/MDNodaRepository.php
@@ -400,12 +400,23 @@ enum MDNodaRepository implements MDValueEnumInterface, JsonSerializable {
     private static function validateIconclassId(string $id):string|false {
 
         if (filter_var($id, FILTER_VALIDATE_URL) !== false) {
-            $id = strtr($id, ['http://iconclass.org/rkd/' => '', 'http://iconclass.org/' => '', 'https://iconclass.org/' => '']);
+            $id = rtrim(strtr($id, [
+                'http://iconclass.org/rkd/' => '',
+                'http://iconclass.org/' => '',
+                'https://iconclass.org/' => '',
+                'http://www.iconclass.org/rkd/' => '',
+                'http://www.iconclass.org/' => '',
+                'https://www.iconclass.org/' => '',
+            ]), '/');
         }
         $id = trim($id, "/");
 
-        if (!empty(trim($id, '0123456789abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ'))) {
-            return false;
+        if (!empty(trim($id, '0123456789abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ(+)'))) {
+            // Try url_decoding
+            $id = urldecode($id);
+            if (!empty(trim($id, '0123456789abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ(+)'))) {
+                return false;
+            }
         }
 
         return $id;
@@ -632,6 +643,29 @@ enum MDNodaRepository implements MDValueEnumInterface, JsonSerializable {
 
     }
 
+    /**
+     * Validates an nomisma ID, returning a string or false.
+     *
+     * @param string $id ID to validate.
+     *
+     * @return string|false
+     */
+    private static function validateNomismaId(string $id):string|false {
+
+        $id = strtr($id, [
+            "http://nomisma.org/id/" => '',
+            "https://nomisma.org/id/" => '',
+        ]);
+
+        // Ensure the remaining string does not contain spaces or slashes
+        foreach (['/', ' '] as $disallowedChar) {
+            if (str_contains($id, $disallowedChar)) return false;
+        }
+
+        return $id;
+
+    }
+
     /**
      * Validates an NPG ID, returning a string or false.
      *
@@ -761,7 +795,7 @@ enum MDNodaRepository implements MDValueEnumInterface, JsonSerializable {
             ]),
             self::ndp_ikmk  => self::validateNdpIkmkForPlaces($id),
             self::ndp_ikmk_persons => self::validateNumericId($id, ['https://ikmk.smb.museum/ndp/person/']),
-            self::nomisma   => self::validateNumericId($id, ['http://nomisma.org/id/']),
+            self::nomisma   => self::validateNomismaId($id),
             self::npg       => self::validateNpgId($id),
             self::oberbegriffsdatei => self::validateNumericId($id, ['https://term.museum-digital.de/oberbegriffsdatei/tag/']),
             self::orcid     => self::validateOrcidId($id),
diff --git a/tests/MDNodaRepositoryTest.php b/tests/MDNodaRepositoryTest.php
index b575e5a..c7dfb12 100644
--- a/tests/MDNodaRepositoryTest.php
+++ b/tests/MDNodaRepositoryTest.php
@@ -408,8 +408,13 @@ final class MDNodaRepositoryTest extends TestCase {
     public static function iconclassIdForValidationProvider():Generator {
 
         yield "45C221 ; url, http" => ["45C221", "http://iconclass.org/rkd/45C221"];
+        yield "45C221 ; url, http, www." => ["45C221", "http://www.iconclass.org/rkd/45C221"];
+        yield "45C221 ; url, http, www., trailing slash" => ["45C221", "http://www.iconclass.org/rkd/45C221/"];
         yield "45C221 ; url, https" => ["45C221", "http://iconclass.org/rkd//45C221"];
+        yield "45C221(+321) ; url, https" => ["45C221(+321)", "http://iconclass.org/rkd//45C221(+321)"];
         yield "45C221 ; ID" => ["45C221", "45C221"];
+        yield "45C221(+321) ; ID" => ["45C221(+321)", "45C221(+321)"];
+        yield "45C221(%2B321) > 45C221(+321) ; ID" => ["45C221(+321)", "45C221(%2B321)"];
         yield "Broken input / adfdasjfklasäj%l" => [false, "adfdasjfklasäj%l"];
 
     }
@@ -429,6 +434,36 @@ final class MDNodaRepositoryTest extends TestCase {
 
     }
 
+    /**
+     * Data provider for validating nomisma entries.
+     *
+     * @return Generator<string, array{0: string|false, 1: string}>
+     */
+    public static function nomismaIdForValidationProvider():Generator {
+
+        yield "1234 (url, https)" => ["1234", "https://nomisma.org/id/1234"];
+        yield "1234" => ["1234", "https://nomisma.org/id/1234"];
+        yield "glass (url, https)" => ["glass", "https://nomisma.org/id/glass"];
+        yield "glass" => ["glass", "glass"];
+        yield "Broken input / empty string" => [false, ""];
+
+    }
+
+    /**
+     * Ensure validating nomisma references.
+     *
+     * @param string|false $expected    Expected output.
+     * @param string       $inputString Input string.
+     *
+     * @return void
+     */
+    #[DataProvider('nomismaIdForValidationProvider')]
+    public function testNomismaIdValidation(string|false $expected, string $inputString):void {
+
+        self::assertEquals($expected, MDNodaRepository::nomisma->validateId($inputString));
+
+    }
+
     /**
      * Tests conversion of already validated and set up entries to strings.
      *