return super().all().annotate(publication_date=Coalesce('published_at', 'created_at')).order_by('-publication_date')
 
     def per_year(self, year):
         return super().all().annotate(publication_date=Coalesce('published_at', 'created_at')).order_by('-publication_date')
 
     def per_year(self, year):