diff --git a/seminar/migrations/0005_alter_problem_autor.py b/seminar/migrations/0005_alter_problem_autor.py
new file mode 100644
index 00000000..264e9848
--- /dev/null
+++ b/seminar/migrations/0005_alter_problem_autor.py
@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+from django.conf import settings
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('seminar', '0004_add_old_dakos_id'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='problem',
+            name='autor',
+            field=models.ForeignKey(related_name='autor_uloh', verbose_name='autor probl\xe9mu', blank=True, to=settings.AUTH_USER_MODEL, null=True),
+            preserve_default=True,
+        ),
+    ]
diff --git a/seminar/migrations/0006_problem_add_timestamp.py b/seminar/migrations/0006_problem_add_timestamp.py
new file mode 100644
index 00000000..3df8bfdb
--- /dev/null
+++ b/seminar/migrations/0006_problem_add_timestamp.py
@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+import datetime
+from django.utils.timezone import utc
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('seminar', '0005_alter_problem_autor'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='problem',
+            name='timestamp',
+            field=models.DateTimeField(default=datetime.datetime(2015, 5, 15, 8, 54, 56, 319985, tzinfo=utc), verbose_name='vytvo\u0159eno', auto_now=True),
+            preserve_default=False,
+        ),
+        migrations.AlterField(
+            model_name='problem',
+            name='dakos_id',
+            field=models.CharField(default=b'', help_text='DaKoS ID z exportu, s prefixem podle p\u016fvodu: "AZAD:xxx (z MM_AZAD), ""DOZ:xxx" (z MM_DOZ), "ZAD:rocnik.cislo.uloha.typ" (z MM_ZADANIA)', max_length=32, verbose_name='Star\xe9 DaKoS ID', blank=True),
+            preserve_default=True,
+        ),
+    ]
diff --git a/seminar/models.py b/seminar/models.py
index 73b52090..a153bc38 100644
--- a/seminar/models.py
+++ b/seminar/models.py
@@ -314,7 +314,7 @@ class Problem(SeminarModelBase):
 
     text_problemu = models.TextField(u'veřejný text zadání a řešení', blank=True)
 
-    autor = models.ForeignKey(settings.AUTH_USER_MODEL, verbose_name=u'autor problému', related_name='autor_uloh')
+    autor = models.ForeignKey(settings.AUTH_USER_MODEL, verbose_name=u'autor problému', related_name='autor_uloh', null=True, blank=True)
 
     opravovatel = models.ForeignKey(settings.AUTH_USER_MODEL, verbose_name=u'opravovatel', null=True, blank=True,
         related_name='opravovatel_uloh')
@@ -329,9 +329,12 @@ class Problem(SeminarModelBase):
 
     body = models.IntegerField(u'maximum bodů', blank=True, null=True)
 
+    timestamp = models.DateTimeField(u'vytvořeno', auto_now=True)
+
     # Staré ID z DAKOSU -- jen u importovaných záznamů
     dakos_id = models.CharField(u'Staré DaKoS ID', max_length=32, blank=True, default='',
-        help_text=u'DaKoS ID z exportu, s prefixem podle původu: "AZAD:xxx" (z MM_AZAD), "DOZ:xxx" (z MM_DOZ), "ZAD:xxx" (z MM_ZADANIA)')
+        help_text=(u'DaKoS ID z exportu, s prefixem podle původu: "AZAD:xxx (z MM_AZAD), "' + 
+        u'"DOZ:xxx" (z MM_DOZ), "ZAD:rocnik.cislo.uloha.typ" (z MM_ZADANIA)'))
 
     def __str__(self):
         return force_unicode(u'%s (%s)' % (self.nazev, self.stav))
@@ -469,9 +472,9 @@ class VysledkyBase(SeminarModelBase):
 
     dummy_id = models.CharField(u'dummy ID pro view', max_length=32, primary_key=True, db_column='id')
 
-    cislo = models.ForeignKey(Cislo, verbose_name=u'číslo pro body', db_column='cislo_id')
+    cislo = models.ForeignKey(Cislo, verbose_name=u'číslo pro body', db_column='cislo_id', on_delete=models.DO_NOTHING)
 
-    resitel = models.ForeignKey(Resitel, verbose_name=u'řešitel', db_column='resitel_id')
+    resitel = models.ForeignKey(Resitel, verbose_name=u'řešitel', db_column='resitel_id', on_delete=models.DO_NOTHING)
 
     body = models.IntegerField(u'body za číslo', db_column='body')