diff --git a/Classes/Domain/Repository/AbstractDatabaseResourceRepository.php b/Classes/Domain/Repository/AbstractDatabaseResourceRepository.php
index f79f885..f6aa497 100644
--- a/Classes/Domain/Repository/AbstractDatabaseResourceRepository.php
+++ b/Classes/Domain/Repository/AbstractDatabaseResourceRepository.php
@@ -20,6 +20,8 @@ abstract class AbstractDatabaseResourceRepository implements ApiResourceReposito
 
     public const ALLOWED_FILTER_OPERATORS = ['eq', 'neq', 'gt', 'gte', 'lt', 'lte', 'in'];
 
+    private const DUPLICATE_IDENTIFIER_SEPARATOR = '#';
+
     /** @var string */
     protected $identifier = self::DEFAULT_IDENTIFIER;
 
@@ -87,7 +89,8 @@ public function findByFiltersWithCursor(array $filters, int $limit, ?string $cur
 
         $result = $query->execute()->fetchAllAssociative();
 
-        $result = $this->resolveOverlay($context, $result);
+        $result = \array_map($this->createDeduplicator(), $result);
+        $result = \array_map($this->createOverlayMapper($context), $result);
 
         $nextCursor = !empty($result) ? \end($result)[$this->identifier] : null;
 
@@ -103,7 +106,7 @@ public function findOneByIdentifier($identifier, $context = null): ?array
 
         $result = $query->execute()->fetchAssociative() ?: [];
 
-        $result = $this->resolveOverlay($context, $result);
+        $result = $this->createOverlayMapper($context)($result);
 
         if ($result) {
             return $this->createMetaMapper()($result);
@@ -119,7 +122,9 @@ public function findByIdentifiers(array $identifiers, $context = null, array $fi
 
         $result = $query->execute()->fetchAllAssociative();
 
-        $result = $this->resolveOverlay($context, $result);
+        $result = \array_map($this->createDeduplicator(), $result);
+
+        $result = \array_map($this->createOverlayMapper($context), $result);
 
         return \array_map($this->createMetaMapper(), $result);
     }
@@ -133,9 +138,26 @@ public function findByPageIdentifier($pageIdentifier): array
 
         // TODO: add overlay?
 
+        $result = \array_map($this->createDeduplicator(), $result);
+
         return \array_map($this->createMetaMapper(), $result);
     }
 
+    protected function createDeduplicator(): \Closure
+    {
+        $countPerId = [];
+        return function (array $resource) use (&$countPerId): array {
+            $identifier = $resource[$this->identifier];
+            $countPerId[$identifier] = isset($countPerId[$identifier]) ? $countPerId[$identifier] + 1 : 0;
+
+            if ($countPerId[$identifier] > 0) {
+                $resource[$this->identifier] = $identifier . self::DUPLICATE_IDENTIFIER_SEPARATOR . $countPerId[$identifier];
+            }
+
+            return $resource;
+        };
+    }
+
     protected function createMetaMapper(): \Closure
     {
         $tableName = $this->tableName;
@@ -155,15 +177,17 @@ protected function createMetaMapper(): \Closure
         };
     }
 
-    protected function resolveOverlay(?Context $context, array $result): array
+    protected function createOverlayMapper(?Context $context): \Closure
     {
-        if (null !== $context && $result) {
-            $pageRepository = GeneralUtility::makeInstance(
-                \TYPO3\CMS\Core\Domain\Repository\PageRepository::class,
-                $context
-            );
-            $overlayResult = $pageRepository->getLanguageOverlay($this->tableName, $result);
-        }
-        return $overlayResult ?? $result;
+        return function (array $resource) use ($context): array {
+            if (null !== $context && $resource) {
+                $pageRepository = GeneralUtility::makeInstance(
+                    \TYPO3\CMS\Core\Domain\Repository\PageRepository::class,
+                    $context
+                );
+                $overlayResult = $pageRepository->getLanguageOverlay($this->tableName, $resource);
+            }
+            return $overlayResult ?? $resource;
+        };
     }
 }
diff --git a/Classes/Domain/Transformer/FileReferenceTransformer.php b/Classes/Domain/Transformer/FileReferenceTransformer.php
index 926820e..cd694ef 100644
--- a/Classes/Domain/Transformer/FileReferenceTransformer.php
+++ b/Classes/Domain/Transformer/FileReferenceTransformer.php
@@ -13,8 +13,6 @@
 
 class FileReferenceTransformer extends TransformerAbstract
 {
-    protected $defaultIncludes = [];
-
     /** @var string */
     protected $identifier;
 
diff --git a/Classes/IncludeHandler/PageRelationIncludeHandler.php b/Classes/IncludeHandler/PageRelationIncludeHandler.php
index 98ca641..0c81a7c 100644
--- a/Classes/IncludeHandler/PageRelationIncludeHandler.php
+++ b/Classes/IncludeHandler/PageRelationIncludeHandler.php
@@ -8,6 +8,7 @@
 use DFAU\ToujouApi\Configuration\ConfigurationManager;
 use DFAU\ToujouApi\Domain\Repository\PageRelationRepository;
 use DFAU\ToujouApi\Domain\Repository\PageRepository;
+use DFAU\ToujouApi\Transformer\ResourceTransformerInterface;
 use League\Fractal\Resource\Collection;
 use League\Fractal\Resource\ResourceInterface;
 use League\Fractal\Scope;
@@ -53,7 +54,7 @@ public function handleInclude(Scope $scope, string $includeName, $data, callable
             throw new \InvalidArgumentException('The given repository "' . \get_class($repository) . '" has to implement the "' . \DFAU\ToujouApi\Domain\Repository\PageRelationRepository::class . '".', 1563210118);
         }
 
-        /** @var ResourceInterface $transformer */
+        /** @var ResourceTransformerInterface $transformer */
         $transformer = $cascader->create($resourceDefinition['transformer'][\Cascader\Cascader::ARGUMENT_CLASS], $resourceDefinition['transformer']);
 
         return new Collection(
diff --git a/Classes/IncludeHandler/TcaResourceIncludeHandler.php b/Classes/IncludeHandler/TcaResourceIncludeHandler.php
index 57ca26c..561c347 100644
--- a/Classes/IncludeHandler/TcaResourceIncludeHandler.php
+++ b/Classes/IncludeHandler/TcaResourceIncludeHandler.php
@@ -6,6 +6,7 @@
 
 use Cascader\Cascader;
 use DFAU\ToujouApi\Configuration\ConfigurationManager;
+use DFAU\ToujouApi\Transformer\ResourceTransformerInterface;
 use League\Fractal\Resource\Collection;
 use League\Fractal\Resource\Item;
 use League\Fractal\Resource\ResourceInterface;
@@ -82,7 +83,7 @@ public function handleInclude(Scope $scope, string $includeName, $data, callable
 
             $repository = $cascader->create($resourceDefinition['repository'][\Cascader\Cascader::ARGUMENT_CLASS], $resourceDefinition['repository']);
 
-            /** @var ResourceInterface $transformer */
+            /** @var ResourceTransformerInterface $transformer */
             $transformer = $cascader->create($resourceDefinition['transformer'][\Cascader\Cascader::ARGUMENT_CLASS], $resourceDefinition['transformer']);
 
             if (Item::class === $resourceType) {
diff --git a/ext_emconf.php b/ext_emconf.php
index 42cc36e..79ae5c7 100755
--- a/ext_emconf.php
+++ b/ext_emconf.php
@@ -15,5 +15,5 @@
         'depends' => [],
         'conflicts' => [],
         'suggests' => [],
-    ]
+    ],
 ];
diff --git a/ext_tables.php b/ext_tables.php
index f68dc3a..0db803d 100644
--- a/ext_tables.php
+++ b/ext_tables.php
@@ -1,22 +1,15 @@
 <?php
 
-defined('TYPO3_MODE') or die();
+\defined('TYPO3_MODE') or die();
 
 $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['toujouApiTcaResource'] = [
-    \TYPO3\CMS\Backend\Form\FormDataProvider\InitializeProcessedTca::class =>
-        $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\InitializeProcessedTca::class],
-    \TYPO3\CMS\Backend\Form\FormDataProvider\DatabaseRecordTypeValue::class =>
-        $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\DatabaseRecordTypeValue::class],
-    \TYPO3\CMS\Backend\Form\FormDataProvider\TcaFlexPrepare::class =>
-        $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\TcaFlexPrepare::class],
-    \TYPO3\CMS\Backend\Form\FormDataProvider\TcaFlexProcess::class =>
-        $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\TcaFlexProcess::class],
-    \TYPO3\CMS\Backend\Form\FormDataProvider\EvaluateDisplayConditions::class =>
-        $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\EvaluateDisplayConditions::class],
-    \TYPO3\CMS\Backend\Form\FormDataProvider\TcaColumnsProcessShowitem::class =>
-        $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\TcaColumnsProcessShowitem::class],
-    \TYPO3\CMS\Backend\Form\FormDataProvider\TcaTypesShowitem::class =>
-        $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\TcaTypesShowitem::class],
+    \TYPO3\CMS\Backend\Form\FormDataProvider\InitializeProcessedTca::class => $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\InitializeProcessedTca::class],
+    \TYPO3\CMS\Backend\Form\FormDataProvider\DatabaseRecordTypeValue::class => $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\DatabaseRecordTypeValue::class],
+    \TYPO3\CMS\Backend\Form\FormDataProvider\TcaFlexPrepare::class => $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\TcaFlexPrepare::class],
+    \TYPO3\CMS\Backend\Form\FormDataProvider\TcaFlexProcess::class => $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\TcaFlexProcess::class],
+    \TYPO3\CMS\Backend\Form\FormDataProvider\EvaluateDisplayConditions::class => $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\EvaluateDisplayConditions::class],
+    \TYPO3\CMS\Backend\Form\FormDataProvider\TcaColumnsProcessShowitem::class => $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\TcaColumnsProcessShowitem::class],
+    \TYPO3\CMS\Backend\Form\FormDataProvider\TcaTypesShowitem::class => $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\TYPO3\CMS\Backend\Form\FormDataProvider\TcaTypesShowitem::class],
     \DFAU\ToujouApi\Form\DatabaseRowDateTimeFields::class => [
         'depends' => [\TYPO3\CMS\Backend\Form\FormDataProvider\InitializeProcessedTca::class],
     ],