text: -- Find the author of the book which has maximum sales.
  
  SELECT A.name
  FROM Author A, Book_Catalog BC, Order_Details OD
  WHERE A.authorid = BC.authorid AND
  	BC.bookid = OD.bookid AND
  	OD.quantity = (
  		SELECT MAX(OD.quantity)
  		FROM Order_Details OD
  	);
  