class Place(models.Model):
    address = models.CharField(max_length=50)
country = models.CharField(max_length=50)


class Publisher(models.Model):
    name = models.CharField(max_length=30)
place = models.OneToOneField(Place, primary_key=True)


class Author(models.Model):
    first_name = models.CharField(max_length=30)
Django OneToOneField, ManyToManyField, Foreign Key