diff --git a/src/Squidex/app/features/content/shared/content-item.component.html b/src/Squidex/app/features/content/shared/content-item.component.html
index 985056255..46fa010eb 100644
--- a/src/Squidex/app/features/content/shared/content-item.component.html
+++ b/src/Squidex/app/features/content/shared/content-item.component.html
@@ -1,7 +1,8 @@
 <td class="cell-select" (click)="stop($event)">
     <ng-container *ngIf="!isReference; else referenceTemplate">
         <input type="checkbox" class="form-check"
-            [ngModel]="selected" 
+            [disabled]="!selectable"
+            [ngModel]="selected || !selectable" 
             (ngModelChange)="selectedChange.emit($event)" />
     </ng-container>
     
diff --git a/src/Squidex/app/features/content/shared/content-item.component.ts b/src/Squidex/app/features/content/shared/content-item.component.ts
index 6e9abe81c..22c0f341f 100644
--- a/src/Squidex/app/features/content/shared/content-item.component.ts
+++ b/src/Squidex/app/features/content/shared/content-item.component.ts
@@ -58,6 +58,9 @@ export class ContentItemComponent implements OnChanges {
     @Input()
     public selected = false;
 
+    @Input()
+    public selectable = false;
+
     @Input()
     public language: AppLanguageDto;
 
diff --git a/src/Squidex/app/features/content/shared/contents-selector.component.html b/src/Squidex/app/features/content/shared/contents-selector.component.html
index 1a745f2d8..384eb28e8 100644
--- a/src/Squidex/app/features/content/shared/contents-selector.component.html
+++ b/src/Squidex/app/features/content/shared/contents-selector.component.html
@@ -16,7 +16,7 @@
                 </sqx-search-form>
             </div>
                 
-            <div class="col pl-1" *ngIf="languages.length > 1">
+            <div class="-auto pl-1" *ngIf="languages.length > 1">
                 <sqx-language-selector class="languages-buttons" (selectedLanguageChange)="selectLanguage($event)" [languages]="languages"></sqx-language-selector>
             </div>
         </div>
@@ -57,6 +57,7 @@
                 <table class="table table-items table-fixed" *ngIf="contentsState.contents | async; let contents">
                     <tbody *ngFor="let content of contents; trackBy: trackByContent">
                         <tr [sqxContent]="content"
+                            [selectable]="!isItemAlreadySelected(content)"
                             [selected]="isItemSelected(content)"
                             (selectedChange)="selectContent(content)"
                             [language]="language"
diff --git a/src/Squidex/app/features/content/shared/contents-selector.component.ts b/src/Squidex/app/features/content/shared/contents-selector.component.ts
index 0c3a2b254..656df7c16 100644
--- a/src/Squidex/app/features/content/shared/contents-selector.component.ts
+++ b/src/Squidex/app/features/content/shared/contents-selector.component.ts
@@ -32,6 +32,12 @@ export class ContentsSelectorComponent implements OnInit {
     @Input()
     public languages: LanguageDto[];
 
+    @Input()
+    public allowDuplicates: boolean;
+
+    @Input()
+    public alreadySelected: ContentDto[];
+
     @Input()
     public schema: SchemaDetailsDto;
 
@@ -76,6 +82,10 @@ export class ContentsSelectorComponent implements OnInit {
         return this.selectedItems[content.id];
     }
 
+    public isItemAlreadySelected(content: ContentDto) {
+        return !this.allowDuplicates && this.alreadySelected && !!this.alreadySelected.find(x => x.id === content.id);
+    }
+
     public emitComplete() {
         this.select.emit([]);
     }
diff --git a/src/Squidex/app/features/content/shared/field-editor.component.html b/src/Squidex/app/features/content/shared/field-editor.component.html
index 3e2082589..791e317d1 100644
--- a/src/Squidex/app/features/content/shared/field-editor.component.html
+++ b/src/Squidex/app/features/content/shared/field-editor.component.html
@@ -128,6 +128,7 @@
                         <ng-container *ngSwitchCase="'List'">
                             <sqx-references-editor
                                 [formControl]="control" 
+                                [allowDuplicates]="field.properties['allowDuplicated']"
                                 [language]="language"
                                 [languages]="languages"
                                 [schemaId]="field.properties['schemaId']"
diff --git a/src/Squidex/app/features/content/shared/references-editor.component.html b/src/Squidex/app/features/content/shared/references-editor.component.html
index 312c46e7f..a935e28bc 100644
--- a/src/Squidex/app/features/content/shared/references-editor.component.html
+++ b/src/Squidex/app/features/content/shared/references-editor.component.html
@@ -29,6 +29,8 @@
 
 <ng-container *sqxModalView="selectorDialog;onRoot:true;closeAuto:false">
     <sqx-contents-selector 
+        [allowDuplicates]="allowDuplicates"
+        [alreadySelected]="snapshot.contentItems"
         [language]="language"
         [languages]="languages"
         [schema]="snapshot.schema"
diff --git a/src/Squidex/app/features/content/shared/references-editor.component.ts b/src/Squidex/app/features/content/shared/references-editor.component.ts
index d394d533c..c25dbc2fe 100644
--- a/src/Squidex/app/features/content/shared/references-editor.component.ts
+++ b/src/Squidex/app/features/content/shared/references-editor.component.ts
@@ -53,6 +53,9 @@ export class ReferencesEditorComponent extends StatefulControlComponent<State, s
     @Input()
     public isCompact = false;
 
+    @Input()
+    public allowDuplicates = true;
+
     public selectorDialog = new DialogModel();
 
     constructor(changeDetector: ChangeDetectorRef,
diff --git a/src/Squidex/app/features/schemas/pages/schema/types/references-ui.component.html b/src/Squidex/app/features/schemas/pages/schema/types/references-ui.component.html
index 3b0b264ba..c901bc7f7 100644
--- a/src/Squidex/app/features/schemas/pages/schema/types/references-ui.component.html
+++ b/src/Squidex/app/features/schemas/pages/schema/types/references-ui.component.html
@@ -4,7 +4,7 @@
 
         <div class="col-9">
             <label class="btn btn-radio" [class.active]="editForm.controls['editor'].value === 'List'">
-                <input type="radio" class="radio-input" name="editor" formControlName="editor" value="Checkbox" />
+                <input type="radio" class="radio-input" name="editor" formControlName="editor" value="List" />
 
                 <i class="icon-control-Checkboxes"></i>