@abc.abstractmethod<EOL><INDENT>def order_book_results(self, book_search_order):<DEDENT>
pass<EOL>
Specify an ordering to the search results.

        :param book_search_order: book search order
        :type book_search_order: ``osid.commenting.BookSearchOrder``
        :raise: ``NullArgument`` -- ``book_search_order`` is ``null``
        :raise: ``Unsupported`` -- ``book_search_order`` is not of this service

        *compliance: mandatory -- This method must be implemented.*