diff --git a/sapl/base/migrations/0019_auto_20180815_1025.py b/sapl/base/migrations/0019_auto_20180815_1025.py
new file mode 100644
index 000000000..e96759e52
--- /dev/null
+++ b/sapl/base/migrations/0019_auto_20180815_1025.py
@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.13 on 2018-08-15 13:25
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('base', '0018_auto_20180801_1652'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='autor',
+            name='tipo',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.PROTECT, to='base.TipoAutor', verbose_name='Tipo do Autor'),
+        ),
+    ]
diff --git a/sapl/base/models.py b/sapl/base/models.py
index fbfadd835..df8ae7c3f 100644
--- a/sapl/base/models.py
+++ b/sapl/base/models.py
@@ -5,6 +5,7 @@ from django.db import models
 from django.db.models.signals import post_migrate
 from django.db.utils import DEFAULT_DB_ALIAS
 from django.utils.translation import ugettext_lazy as _
+
 from sapl.utils import (LISTA_DE_UFS, YES_NO_CHOICES,
                         get_settings_auth_user_model, models_with_gr_for_model)
 
@@ -178,7 +179,8 @@ class Autor(models.Model):
                                 on_delete=models.SET_NULL,
                                 null=True)
 
-    tipo = models.ForeignKey(TipoAutor, verbose_name=_('Tipo do Autor'))
+    tipo = models.ForeignKey(TipoAutor, verbose_name=_('Tipo do Autor'),
+                             on_delete=models.PROTECT)
 
     content_type = models.ForeignKey(
         ContentType,
@@ -199,23 +201,17 @@ class Autor(models.Model):
         ordering = ('nome',)
 
     def __str__(self):
-
         if self.autor_related:
             return str(self.autor_related)
         else:
-            if str(self.cargo):
-                return _('%(nome)s - %(cargo)s') % {
-                    'nome': self.nome, 'cargo': self.cargo}
-            else:
-                return str(self.nome)
-        """if str(self.tipo) == 'Parlamentar' and self.parlamentar:
-            return self.parlamentar.nome_parlamentar
-        elif str(self.tipo) == 'Comissao' and self.comissao:
-            return str(self.comissao)
-        elif str(self.tipo) == 'Partido' and self.partido:
-            return str(self.partido)
-        else:
-        """
+            if self.nome:
+                if self.cargo:
+                    return '{} - {}'.format(self.nome, self.cargo)
+                else:
+                    return str(self.nome)
+        if self.user:
+            return str(self.user.username)
+        return '?'
 
 
 def cria_models_tipo_autor(app_config=None, verbosity=2, interactive=True,
diff --git a/sapl/crud/base.py b/sapl/crud/base.py
index 8bb8c3794..739fc4f37 100644
--- a/sapl/crud/base.py
+++ b/sapl/crud/base.py
@@ -851,7 +851,9 @@ class CrudDeleteView(PermissionRequiredContainerCrudMixin,
                          é referenciado por outros registros:<br>\
                          <ul>'
             for i in err.protected_objects:
-                error_msg += '<li>' + i.__str__() + '</li>'
+                error_msg += '<li>{} - {}</li>'.format(
+                    i._meta.verbose_name, i
+                )
             error_msg += '</ul>'
 
             messages.add_message(request,