diff --git a/app/Http/Controllers/Publish/IndexController.php b/app/Http/Controllers/Publish/IndexController.php
index c1dded3..2639dbf 100644
--- a/app/Http/Controllers/Publish/IndexController.php
+++ b/app/Http/Controllers/Publish/IndexController.php
@@ -479,8 +479,13 @@ class IndexController extends Controller
                 //save keywords
                 if (isset($data['keywords'])) {
                     foreach ($request->get('keywords') as $key => $keyword) {
-                        $dataKeyword = new Subject($keyword);
-                        $dataset->subjects()->save($dataKeyword);
+                        // $dataKeyword = new Subject($keyword);
+                        // $dataset->subjects()->save($dataKeyword);                       
+                        $keyword = Subject::firstOrCreate(
+                            ['value' => $keyword['value']],
+                            $keyword
+                        );
+                        $dataset->subjects()->attach($keyword);
                     }
                 }
 
diff --git a/app/Library/Xml/DatasetExtension.php b/app/Library/Xml/DatasetExtension.php
index 317e151..e17c423 100644
--- a/app/Library/Xml/DatasetExtension.php
+++ b/app/Library/Xml/DatasetExtension.php
@@ -78,6 +78,7 @@ trait DatasetExtension
         ),
         'Subject' => array(
             'model' => Subject::class,
+            'through' => 'link_dataset_subjects',
             'relation' => 'subjects',
             'fetch' => 'eager'
         ),
diff --git a/app/Models/Dataset.php b/app/Models/Dataset.php
index e465884..16efd2f 100644
--- a/app/Models/Dataset.php
+++ b/app/Models/Dataset.php
@@ -260,9 +260,13 @@ class Dataset extends Model
         return $this->hasMany(\App\Models\DatasetReference::class, 'document_id', 'id');
     }
 
+    // public function subjects()
+    // {
+    //     return $this->hasMany(\App\Models\Subject::class, 'document_id', 'id');
+    // }
     public function subjects()
     {
-        return $this->hasMany(\App\Models\Subject::class, 'document_id', 'id');
+        return $this->belongsToMany(\App\Models\Subject::class, 'link_dataset_subjects', 'document_id', 'subject_id');
     }
 
     /**
diff --git a/app/Models/Subject.php b/app/Models/Subject.php
index c992e2c..7223ec7 100644
--- a/app/Models/Subject.php
+++ b/app/Models/Subject.php
@@ -7,13 +7,18 @@ use App\Models\Dataset;
 
 class Subject extends Model
 {
-    protected $table = 'document_subjects';
+    // protected $table = 'document_subjects';
+    protected $table = 'dataset_subjects';
     public $timestamps = false;
 
     protected $fillable = ['value', 'type', 'language'];
 
-    public function dataset()
+    // public function dataset()
+    // {
+    //     return $this->belongsTo(Dataset::class, 'document_id', 'id');
+    // }
+    public function datasets()
     {
-        return $this->belongsTo(Dataset::class, 'document_id', 'id');
+        return $this->belongsToMany(Dataset::class, 'link_dataset_subjects', 'subject_id', 'document_id');
     }
 }
diff --git a/composer.lock b/composer.lock
index 0536396..d75b9a4 100755
--- a/composer.lock
+++ b/composer.lock
@@ -3870,16 +3870,16 @@
         },
         {
             "name": "symfony/http-foundation",
-            "version": "v5.3.0",
+            "version": "v5.3.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/http-foundation.git",
-                "reference": "31f25d99b329a1461f42bcef8505b54926a30be6"
+                "reference": "8827b90cf8806e467124ad476acd15216c2fceb6"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/http-foundation/zipball/31f25d99b329a1461f42bcef8505b54926a30be6",
-                "reference": "31f25d99b329a1461f42bcef8505b54926a30be6",
+                "url": "https://api.github.com/repos/symfony/http-foundation/zipball/8827b90cf8806e467124ad476acd15216c2fceb6",
+                "reference": "8827b90cf8806e467124ad476acd15216c2fceb6",
                 "shasum": ""
             },
             "require": {
@@ -3923,7 +3923,7 @@
             "description": "Defines an object-oriented layer for the HTTP specification",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/http-foundation/tree/v5.3.0"
+                "source": "https://github.com/symfony/http-foundation/tree/v5.3.1"
             },
             "funding": [
                 {
@@ -3939,20 +3939,20 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-05-26T17:43:10+00:00"
+            "time": "2021-06-02T09:32:00+00:00"
         },
         {
             "name": "symfony/http-kernel",
-            "version": "v5.3.0",
+            "version": "v5.3.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/http-kernel.git",
-                "reference": "f8e8f5391b6909e2f0ba8c12220ab7af3050eb4f"
+                "reference": "74eb022e3bac36b3d3a897951a98759f2b32b864"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/http-kernel/zipball/f8e8f5391b6909e2f0ba8c12220ab7af3050eb4f",
-                "reference": "f8e8f5391b6909e2f0ba8c12220ab7af3050eb4f",
+                "url": "https://api.github.com/repos/symfony/http-kernel/zipball/74eb022e3bac36b3d3a897951a98759f2b32b864",
+                "reference": "74eb022e3bac36b3d3a897951a98759f2b32b864",
                 "shasum": ""
             },
             "require": {
@@ -4035,7 +4035,7 @@
             "description": "Provides a structured process for converting a Request into a Response",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/http-kernel/tree/v5.3.0"
+                "source": "https://github.com/symfony/http-kernel/tree/v5.3.1"
             },
             "funding": [
                 {
@@ -4051,7 +4051,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-05-31T10:44:03+00:00"
+            "time": "2021-06-02T10:07:12+00:00"
         },
         {
             "name": "symfony/mime",
@@ -6515,16 +6515,16 @@
         },
         {
             "name": "phpunit/phpunit",
-            "version": "9.5.4",
+            "version": "9.5.5",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit.git",
-                "reference": "c73c6737305e779771147af66c96ca6a7ed8a741"
+                "reference": "89ff45ea9d70e35522fb6654a2ebc221158de276"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/c73c6737305e779771147af66c96ca6a7ed8a741",
-                "reference": "c73c6737305e779771147af66c96ca6a7ed8a741",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/89ff45ea9d70e35522fb6654a2ebc221158de276",
+                "reference": "89ff45ea9d70e35522fb6654a2ebc221158de276",
                 "shasum": ""
             },
             "require": {
@@ -6554,7 +6554,7 @@
                 "sebastian/global-state": "^5.0.1",
                 "sebastian/object-enumerator": "^4.0.3",
                 "sebastian/resource-operations": "^3.0.3",
-                "sebastian/type": "^2.3",
+                "sebastian/type": "^2.3.2",
                 "sebastian/version": "^3.0.2"
             },
             "require-dev": {
@@ -6602,7 +6602,7 @@
             ],
             "support": {
                 "issues": "https://github.com/sebastianbergmann/phpunit/issues",
-                "source": "https://github.com/sebastianbergmann/phpunit/tree/9.5.4"
+                "source": "https://github.com/sebastianbergmann/phpunit/tree/9.5.5"
             },
             "funding": [
                 {
@@ -6614,7 +6614,7 @@
                     "type": "github"
                 }
             ],
-            "time": "2021-03-23T07:16:29+00:00"
+            "time": "2021-06-05T04:49:07+00:00"
         },
         {
             "name": "sebastian/cli-parser",
@@ -7473,16 +7473,16 @@
         },
         {
             "name": "sebastian/type",
-            "version": "2.3.1",
+            "version": "2.3.2",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/type.git",
-                "reference": "81cd61ab7bbf2de744aba0ea61fae32f721df3d2"
+                "reference": "0d1c587401514d17e8f9258a27e23527cb1b06c1"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/type/zipball/81cd61ab7bbf2de744aba0ea61fae32f721df3d2",
-                "reference": "81cd61ab7bbf2de744aba0ea61fae32f721df3d2",
+                "url": "https://api.github.com/repos/sebastianbergmann/type/zipball/0d1c587401514d17e8f9258a27e23527cb1b06c1",
+                "reference": "0d1c587401514d17e8f9258a27e23527cb1b06c1",
                 "shasum": ""
             },
             "require": {
@@ -7517,7 +7517,7 @@
             "homepage": "https://github.com/sebastianbergmann/type",
             "support": {
                 "issues": "https://github.com/sebastianbergmann/type/issues",
-                "source": "https://github.com/sebastianbergmann/type/tree/2.3.1"
+                "source": "https://github.com/sebastianbergmann/type/tree/2.3.2"
             },
             "funding": [
                 {
@@ -7525,7 +7525,7 @@
                     "type": "github"
                 }
             ],
-            "time": "2020-10-26T13:18:59+00:00"
+            "time": "2021-06-04T13:02:07+00:00"
         },
         {
             "name": "sebastian/version",
@@ -7701,5 +7701,5 @@
     "platform-overrides": {
         "php": "7.3"
     },
-    "plugin-api-version": "2.0.0"
+    "plugin-api-version": "2.1.0"
 }
diff --git a/database/migrations/2021_06_07_135923_create_dataset_subjects_table.php b/database/migrations/2021_06_07_135923_create_dataset_subjects_table.php
new file mode 100644
index 0000000..232afa3
--- /dev/null
+++ b/database/migrations/2021_06_07_135923_create_dataset_subjects_table.php
@@ -0,0 +1,58 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class CreateDatasetSubjects extends Migration
+{
+    // php artisan make:migration create_dataset_subjects_table --table=dataset_subjects --create=dataset_subjects
+// php artisan migrate
+
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('dataset_subjects', function (Blueprint $table) {
+            $table->id();
+            $table->string('language', 3)->nullable();
+            $table->enum(
+                'type',
+                ['uncontrolled']
+            );
+            $table->string('value', 255);
+            $table->string('external_key', 255)->nullable();
+            $table->nullableTimestamps();
+        });
+
+        Schema::create('link_dataset_subjects', function (Blueprint $table) {
+            // $table->increments('id');
+
+            $table->unsignedInteger('subject_id')->index();
+            $table->foreign('subject_id')
+                ->references('id')->on('dataset_subjects')
+                ->onDelete('no action')->onUpdate('no action'); //detach the relation via code
+
+            $table->unsignedInteger('document_id')->index();
+            $table->foreign('document_id')
+                ->references('id')->on('documents')
+                ->onDelete('cascade')->onUpdate('cascade');
+
+            $table->primary(['subject_id', 'document_id']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('link_dataset_subjects');
+        Schema::dropIfExists('dataset_subjects');
+    }
+}
diff --git a/routes/api.php b/routes/api.php
index 1cb690f..15cf0b7 100644
--- a/routes/api.php
+++ b/routes/api.php
@@ -14,8 +14,11 @@ use App\Models\Person;
 | is assigned the "api" middleware group. Enjoy building your API!
 |
 */
+$base_domain = config('app.url');
+$alias_domain = config('app.alias_url');
 
-Route::domain('tethys.at')->group(function () {
+// Route::domain('tethys.at')->group(function () {
+$appRoutes = function () {
     
     Route::match(array('GET', 'POST'), '/oai', ['as' => 'oai', 'uses' => 'Oai\RequestController@index']);
 
@@ -79,4 +82,9 @@ Route::domain('tethys.at')->group(function () {
             ->header('Access-Control-Allow-Origin', '*')
             ->header('Access-Control-Allow-Methods', 'GET');
     });
-});
+};
+
+Route::group(array('domain' => $base_domain), $appRoutes);
+if ($alias_domain) {
+    Route::group(array('domain' => $alias_domain), $appRoutes);
+}