diff --git a/db.sqlite3 b/db.sqlite3
index 159deb30..ec6f8a59 100644
Binary files a/db.sqlite3 and b/db.sqlite3 differ
diff --git a/django_api/__pycache__/models.cpython-39.pyc b/django_api/__pycache__/models.cpython-39.pyc
index 6e03f906..cdfe3878 100644
Binary files a/django_api/__pycache__/models.cpython-39.pyc and b/django_api/__pycache__/models.cpython-39.pyc differ
diff --git a/django_api/models.py b/django_api/models.py
index 8f6ae63a..5a21128c 100644
--- a/django_api/models.py
+++ b/django_api/models.py
@@ -1,166 +1,166 @@
 from django.db import models
 from django.contrib.auth.models import User
 
 from datetime import date
 from django.utils.translation import gettext as _
 
 
 # test model with essential tables 
 
 
 class Country(models.Model):
-     name = models.CharField(max_length = 120, null=False, default='unknown')
-     iso_code = models.CharField(max_length = 3, null=False, default='unknown')
+     name = models.CharField(max_length = 120, null=True)
+     iso_code = models.CharField(max_length = 3, null=True)
      
      def __str__(self):
          return f"{self.name}"
      
      class Meta:
          ordering = ('name',)
 
 class City(models.Model):
-     name = models.CharField(max_length = 120, null=False, default='unknown')
-     iso_code = models.CharField(max_length = 3, null=False, default='unknown')
-     state = models.CharField(max_length = 3, null=False, default='unknown')
+     name = models.CharField(max_length = 120, null=True)
+     iso_code = models.CharField(max_length = 3, null=True)
+     state = models.CharField(max_length = 3, null=True)
 
      def __str__(self):
         return f"{self.name}"
     
      class Meta:
          ordering = ('name',)
 
 class Language(models.Model):
-    name = models.CharField(max_length = 120, null=False, default='unknown')
-    iso_code = models.CharField(max_length = 3, null=False, default='unknown')
+    name = models.CharField(max_length = 120, null=True)
+    iso_code = models.CharField(max_length = 3, null=True)
 
     def __str__(self):
         return f"{self.name}"
     
     class Meta:
         ordering = ('name',)
 
 
 class Issn(models.Model):
     PRINT = 1
     ELECTRONIC = 2
     CDROM = 3
 
     TYPE_CHOICES = (
         (PRINT, 'Print'),
         (ELECTRONIC, 'Electronic'),
         (CDROM, 'CD-ROM'),
     )
     
     
     nbr = models.CharField(max_length = 9, null=False)
     journal = models.ManyToManyField("Journal") # search journal with ISSN
     type_list = models.CharField(
         choices = TYPE_CHOICES,
         max_length=10,
         blank=True
     )
 
     
 
     def __str__(self):
         return f"{self.nbr} for {self.type_list}"
     
     class Meta:
         ordering = ('nbr',)
 
 class Oa(models.Model):
-    status = models.CharField(max_length=1000, null=False, default='unknown')
-    description = models.CharField(max_length=1000, null=False, default='unknown')
+    status = models.CharField(max_length=1000, null=True)
+    description = models.CharField(max_length=1000, null=True)
     subscription = models.BooleanField(default=False)
     accepted_manuscript = models.BooleanField(default=False)
     apc = models.BooleanField(default=False)
     final_version = models.BooleanField(default=False)
 
     def __str__(self):
         return f"{self.status}"
 
     class Meta:
         ordering = ('subscription',)
 
 class Publisher(models.Model):
-    name = models.CharField(max_length=1000, null=False, default='unknown')
+    name = models.CharField(max_length=1000, null=True)
     # city = models.ManyToManyField("City")
-    city = models.CharField(max_length=100, null=False, default='unknown')
+    city = models.CharField(max_length=100, null=True)
     state = models.CharField(max_length = 3, null=True)
     country = models.ManyToManyField("Country")
     starting_year = models.PositiveIntegerField()
     website = models.URLField(max_length=1000)
     oa_policies_url = models.URLField(max_length=1000)
 
     def __str__(self):
         return f"{self.name}"
     
     class Meta:
         ordering = ('name',)
 
 class Journal(models.Model):
-    name = models.CharField(max_length=1000, null=False) # search journal with name
-    name_short_iso_4 = models.CharField(max_length=300, null=False)
+    name = models.CharField(max_length=1000, null=True) # search journal with name
+    name_short_iso_4 = models.CharField(max_length=300, null=True)
     publisher = models.ManyToManyField(Publisher)
     website = models.URLField(max_length=300)
     # issn = models.ManyToManyField("Issn") # search journal with ISSN
     oa_options_url = models.URLField(max_length=1000)
     oa_status = models.ForeignKey("Oa", on_delete=models.CASCADE)
     starting_year = models.PositiveIntegerField()
 
  
     def __str__(self):
         return f"{self.name} from {self.website}"
     
     class Meta:
         ordering = ('name',)
 
 class Institution(models.Model):
     name_en = models.CharField(max_length=1000, null=True)
     name_en_short = models.CharField(max_length=100, null=True)
     name_de = models.CharField(max_length=1000, null=True)
     name_de_short = models.CharField(max_length=100, null=True)
     name_fr = models.CharField(max_length=1000, null=True)
     name_fr_short = models.CharField(max_length=100, null=True)
     name_it = models.CharField(max_length=1000, null=True)
     name_it_short = models.CharField(max_length=100, null=True)
     website = models.URLField(max_length=300)
     country = models.ManyToManyField("Country")
     starting_year = models.PositiveIntegerField()
 
 
 
 
 
 
 
 
 
     def __str__(self):
         return f"{self.website}"
     
     class Meta:
         ordering = ('starting_year',)
 
 class Funder(models.Model):
-    name = models.CharField(max_length=300, null=False)
+    name = models.CharField(max_length=300, null=True)
 
     def __str__(self):
         return f"{self.name}"
     
     class Meta:
         ordering = ('name',)
 
 class Condition(models.Model):
     name = models.CharField(max_length=300, null=False)
     validity = models.DateField(_("Date"), default=date.today) # add today for testing purpose
     journal = models.ManyToManyField(Journal)
     funder = models.ManyToManyField(Funder)
     institution = models.ManyToManyField(Institution)
 
     class Meta:
         ordering = ('-validity',)
     
     def __str__(self):
         return f"{self.name}"