diff --git a/rsconcept/backend/apps/rsform/admin.py b/rsconcept/backend/apps/rsform/admin.py
index c5dbafd1..c8e238c6 100644
--- a/rsconcept/backend/apps/rsform/admin.py
+++ b/rsconcept/backend/apps/rsform/admin.py
@@ -10,7 +10,8 @@ class ConstituentaAdmin(admin.ModelAdmin):
     list_display = ['schema', 'alias', 'term_resolved', 'definition_resolved']
     search_fields = ['term_resolved', 'definition_resolved']
 
-class LibraryAdmin(admin.ModelAdmin):
+
+class LibraryItemAdmin(admin.ModelAdmin):
     ''' Admin model: LibraryItem. '''
     date_hierarchy = 'time_update'
     list_display = [
@@ -22,6 +23,18 @@ class LibraryAdmin(admin.ModelAdmin):
     search_fields = ['alias', 'title']
 
 
+class LibraryTemplateAdmin(admin.ModelAdmin):
+    ''' Admin model: LibraryTemplate. '''
+    list_display = ['id', 'alias']
+    list_select_related = ['lib_source']
+
+    def alias(self, template: models.LibraryTemplate):
+        if template.lib_source:
+            return template.lib_source.alias
+        else:
+            return 'N/A'
+
+
 class SubscriptionAdmin(admin.ModelAdmin):
     ''' Admin model: Subscriptions. '''
     list_display = ['id', 'item', 'user']
@@ -32,5 +45,6 @@ class SubscriptionAdmin(admin.ModelAdmin):
 
 
 admin.site.register(models.Constituenta, ConstituentaAdmin)
-admin.site.register(models.LibraryItem, LibraryAdmin)
+admin.site.register(models.LibraryItem, LibraryItemAdmin)
+admin.site.register(models.LibraryTemplate, LibraryTemplateAdmin)
 admin.site.register(models.Subscription, SubscriptionAdmin)
diff --git a/rsconcept/backend/apps/rsform/migrations/0002_librarytemplate.py b/rsconcept/backend/apps/rsform/migrations/0002_librarytemplate.py
new file mode 100644
index 00000000..00bc2699
--- /dev/null
+++ b/rsconcept/backend/apps/rsform/migrations/0002_librarytemplate.py
@@ -0,0 +1,25 @@
+# Generated by Django 4.2.6 on 2023-10-18 16:12
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('rsform', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='LibraryTemplate',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('lib_source', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='rsform.libraryitem', verbose_name='Источник')),
+            ],
+            options={
+                'verbose_name': 'Шаблон',
+                'verbose_name_plural': 'Шаблоны',
+            },
+        ),
+    ]
diff --git a/rsconcept/backend/apps/rsform/models.py b/rsconcept/backend/apps/rsform/models.py
index 32b4957a..2a63df61 100644
--- a/rsconcept/backend/apps/rsform/models.py
+++ b/rsconcept/backend/apps/rsform/models.py
@@ -71,8 +71,7 @@ def _get_type_prefix(cst_type: CstType) -> str:
 
 
 class LibraryItem(Model):
-    ''' Abstract library item.
-        Please use wrappers below to access functionality. '''
+    ''' Abstract library item.'''
     item_type: CharField = CharField(
         verbose_name='Тип',
         max_length=50,
@@ -136,6 +135,21 @@ class LibraryItem(Model):
             Subscription.subscribe(user=self.owner, item=self)
 
 
+class LibraryTemplate(Model):
+    ''' Template for library items and constituents. '''
+    lib_source: ForeignKey = ForeignKey(
+        verbose_name='Источник',
+        to=LibraryItem,
+        on_delete=CASCADE,
+        null=True
+    )
+
+    class Meta:
+        ''' Model metadata. '''
+        verbose_name = 'Шаблон'
+        verbose_name_plural = 'Шаблоны'
+
+
 class Subscription(Model):
     ''' User subscription to library item. '''
     user: ForeignKey = ForeignKey(
@@ -319,6 +333,8 @@ class RSForm:
         ''' Insert new constituenta at given position. All following constituents order is shifted by 1 position '''
         if position <= 0:
             raise ValidationError('Invalid position: should be positive integer')
+        if self.constituents().filter(alias=alias).exists():
+            raise ValidationError(f'Alias taken {alias}')
         currentSize = self.constituents().count()
         position =  max(1, min(position, currentSize + 1))
         update_list = \
@@ -342,6 +358,8 @@ class RSForm:
     @transaction.atomic
     def insert_last(self, alias: str, insert_type: CstType) -> 'Constituenta':
         ''' Insert new constituenta at last position '''
+        if self.constituents().filter(alias=alias).exists():
+            raise ValidationError(f'Alias taken {alias}')
         position = 1
         if self.constituents().exists():
             position += self.constituents().count()
diff --git a/rsconcept/backend/apps/rsform/serializers.py b/rsconcept/backend/apps/rsform/serializers.py
index c6204ec0..6a786e7a 100644
--- a/rsconcept/backend/apps/rsform/serializers.py
+++ b/rsconcept/backend/apps/rsform/serializers.py
@@ -188,13 +188,18 @@ class CstRenameSerializer(serializers.ModelSerializer):
     def validate(self, attrs):
         schema = cast(RSForm, self.context['schema'])
         old_cst = Constituenta.objects.get(pk=self.initial_data['id'])
+        new_alias = self.initial_data['alias']
         if old_cst.schema != schema.item:
             raise serializers.ValidationError({
                 'id': f'Изменяемая конституента должна относиться к изменяемой схеме: {schema.item.title}'
             })
-        if old_cst.alias == self.initial_data['alias']:
+        if old_cst.alias == new_alias:
             raise serializers.ValidationError({
-                'alias': f'Имя конституенты должно отличаться от текущего: {self.initial_data["alias"]}'
+                'alias': f'Имя конституенты должно отличаться от текущего: {new_alias}'
+            })
+        if schema.constituents().filter(alias=new_alias).exists():
+            raise serializers.ValidationError({
+                'alias': f'Конституента с таким именем уже существует: {new_alias}'
             })
         self.instance = old_cst
         attrs['schema'] = schema.item
diff --git a/rsconcept/backend/apps/rsform/tests/t_models.py b/rsconcept/backend/apps/rsform/tests/t_models.py
index 43834ce1..838d673c 100644
--- a/rsconcept/backend/apps/rsform/tests/t_models.py
+++ b/rsconcept/backend/apps/rsform/tests/t_models.py
@@ -190,9 +190,17 @@ class TestRSForm(TestCase):
         self.assertEqual(cst2.order, 1)
         self.assertEqual(cst1.order, 2)
 
+    def test_insert_at_invalid_position(self):
+        schema = RSForm.create(title='Test')
         with self.assertRaises(ValidationError):
             schema.insert_at(0, 'X5', CstType.BASE)
 
+    def test_insert_at_invalid_alias(self):
+        schema = RSForm.create(title='Test')
+        schema.insert_at(1, 'X1', CstType.BASE)
+        with self.assertRaises(ValidationError):
+            schema.insert_at(2, 'X1', CstType.BASE)
+
     def test_insert_at_reorder(self):
         schema = RSForm.create(title='Test')
         schema.insert_at(1, 'X1', CstType.BASE)
diff --git a/rsconcept/backend/apps/rsform/tests/t_views.py b/rsconcept/backend/apps/rsform/tests/t_views.py
index 38218cd2..382557b3 100644
--- a/rsconcept/backend/apps/rsform/tests/t_views.py
+++ b/rsconcept/backend/apps/rsform/tests/t_views.py
@@ -8,7 +8,10 @@ from rest_framework.exceptions import ErrorDetail
 from cctext import ReferenceType, split_grams
 
 from apps.users.models import User
-from apps.rsform.models import Syntax, RSForm, Constituenta, CstType, LibraryItem, LibraryItemType, Subscription
+from apps.rsform.models import (
+  Syntax, RSForm, Constituenta, CstType,
+  LibraryItem, LibraryItemType, Subscription, LibraryTemplate
+)
 from apps.rsform.views import (
     convert_to_ascii,
     convert_to_math,
@@ -264,6 +267,20 @@ class TestLibraryViewset(APITestCase):
         self.assertEqual(response.status_code, 204)
         self.assertFalse(self.user in self.unowned.subscribers())
 
+    def test_retrieve_templates(self):
+        response = self.client.get('/api/library/templates')
+        self.assertEqual(response.status_code, 200)
+        self.assertFalse(_response_contains(response, self.common))
+        self.assertFalse(_response_contains(response, self.unowned))
+        self.assertFalse(_response_contains(response, self.owned))
+
+        LibraryTemplate.objects.create(lib_source=self.unowned)
+        response = self.client.get('/api/library/templates')
+        self.assertEqual(response.status_code, 200)
+        self.assertFalse(_response_contains(response, self.common))
+        self.assertTrue(_response_contains(response, self.unowned))
+        self.assertFalse(_response_contains(response, self.owned))
+
 
 class TestRSFormViewset(APITestCase):
     ''' Testing RSForm view. '''
@@ -420,22 +437,22 @@ class TestRSFormViewset(APITestCase):
         self.assertEqual(x4.order, 3)
 
     def test_rename_constituenta(self):
-        self.cst1 = Constituenta.objects.create(
+        cst1 = Constituenta.objects.create(
             alias='X1', schema=self.owned.item, order=1, convention='Test',
             term_raw='Test1', term_resolved='Test1',
             term_forms=[{'text':'form1', 'tags':'sing,datv'}]
         )
-        self.cst2 = Constituenta.objects.create(
+        cst2 = Constituenta.objects.create(
             alias='X2', schema=self.unowned.item, order=1, convention='Test1',
             term_raw='Test2', term_resolved='Test2'
         )
-        self.cst3 = Constituenta.objects.create(
+        cst3 = Constituenta.objects.create(
             alias='X3', schema=self.owned.item, order=2,
             term_raw='Test3', term_resolved='Test3',
             definition_raw='Test1', definition_resolved='Test2'
         )
         
-        data = {'alias': 'D2', 'cst_type': 'term', 'id': self.cst2.pk}
+        data = {'alias': 'D2', 'cst_type': 'term', 'id': cst2.pk}
         response = self.client.patch(
             f'/api/rsforms/{self.unowned.item.id}/cst-rename',
             data=data, format='json'
@@ -448,14 +465,21 @@ class TestRSFormViewset(APITestCase):
         )
         self.assertEqual(response.status_code, 400)
 
-        data = {'alias': self.cst1.alias, 'cst_type': 'term', 'id': self.cst1.pk}
+        data = {'alias': cst1.alias, 'cst_type': 'term', 'id': cst1.pk}
         response = self.client.patch(
             f'/api/rsforms/{self.owned.item.id}/cst-rename',
             data=data, format='json'
         )
         self.assertEqual(response.status_code, 400)
 
-        data = {'alias': 'D2', 'cst_type': 'term', 'id': self.cst1.pk}
+        data = {'alias': cst3.alias, 'id': cst1.pk}
+        response = self.client.patch(
+            f'/api/rsforms/{self.owned.item.id}/cst-rename',
+            data=data, format='json'
+        )
+        self.assertEqual(response.status_code, 400)
+
+        data = {'alias': 'D2', 'cst_type': 'term', 'id': cst1.pk}
         item = self.owned.item
         d1 = Constituenta.objects.create(schema=item, alias='D1', cst_type='term', order=4)
         d1.term_raw = '@{X1|plur}'
@@ -463,9 +487,9 @@ class TestRSFormViewset(APITestCase):
         d1.save()
         
         self.assertEqual(d1.order, 4)
-        self.assertEqual(self.cst1.order, 1)
-        self.assertEqual(self.cst1.alias, 'X1')
-        self.assertEqual(self.cst1.cst_type, CstType.BASE)
+        self.assertEqual(cst1.order, 1)
+        self.assertEqual(cst1.alias, 'X1')
+        self.assertEqual(cst1.cst_type, CstType.BASE)
         response = self.client.patch(
             f'/api/rsforms/{item.id}/cst-rename',
             data=data, format='json'
@@ -474,13 +498,13 @@ class TestRSFormViewset(APITestCase):
         self.assertEqual(response.data['new_cst']['alias'], 'D2')
         self.assertEqual(response.data['new_cst']['cst_type'], 'term')
         d1.refresh_from_db()
-        self.cst1.refresh_from_db()
+        cst1.refresh_from_db()
         self.assertEqual(d1.order, 4)
         self.assertEqual(d1.term_resolved, '')
         self.assertEqual(d1.term_raw,  '@{D2|plur}')
-        self.assertEqual(self.cst1.order, 1)
-        self.assertEqual(self.cst1.alias, 'D2')
-        self.assertEqual(self.cst1.cst_type, CstType.TERM)
+        self.assertEqual(cst1.order, 1)
+        self.assertEqual(cst1.alias, 'D2')
+        self.assertEqual(cst1.cst_type, CstType.TERM)
 
     def test_create_constituenta_data(self):
         data = {
diff --git a/rsconcept/backend/apps/rsform/urls.py b/rsconcept/backend/apps/rsform/urls.py
index bc4aac7a..71640190 100644
--- a/rsconcept/backend/apps/rsform/urls.py
+++ b/rsconcept/backend/apps/rsform/urls.py
@@ -9,6 +9,7 @@ library_router.register('rsforms', views.RSFormViewSet)
 
 urlpatterns = [
     path('library/active', views.LibraryActiveView.as_view(), name='library'),
+    path('library/templates', views.LibraryTemplatesView.as_view(), name='library'),
     path('constituents/<int:pk>', views.ConstituentAPIView.as_view(), name='constituenta-detail'),
     path('rsforms/import-trs', views.TrsImportView.as_view()),
     path('rsforms/create-detailed', views.create_rsform),
diff --git a/rsconcept/backend/apps/rsform/views.py b/rsconcept/backend/apps/rsform/views.py
index f8527479..f8ef7dd4 100644
--- a/rsconcept/backend/apps/rsform/views.py
+++ b/rsconcept/backend/apps/rsform/views.py
@@ -22,7 +22,7 @@ from . import utils
 @extend_schema(tags=['Library'])
 @extend_schema_view()
 class LibraryActiveView(generics.ListAPIView):
-    ''' Endpoint: Get list of rsforms available for active user. '''
+    ''' Endpoint: Get list of library items available for active user. '''
     permission_classes = (permissions.AllowAny,)
     serializer_class = s.LibraryItemSerializer
 
@@ -35,6 +35,18 @@ class LibraryActiveView(generics.ListAPIView):
             ).distinct().order_by('-time_update')
         else:
             return m.LibraryItem.objects.filter(is_common=True).order_by('-time_update')
+        
+
+@extend_schema(tags=['Library'])
+@extend_schema_view()
+class LibraryTemplatesView(generics.ListAPIView):
+    ''' Endpoint: Get list of templates. '''
+    permission_classes = (permissions.AllowAny,)
+    serializer_class = s.LibraryItemSerializer
+
+    def get_queryset(self):
+        template_ids = m.LibraryTemplate.objects.values_list('lib_source', flat=True)
+        return m.LibraryItem.objects.filter(pk__in=template_ids)
 
 
 @extend_schema(tags=['Constituenta'])