Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
--------
Question: The site of the 1461 Battle of Mortimer's Cross lies in which English county?

Answer: battle of mortimer's cross


Question: Which major river has its source at the confluence of the rivers Brigach and Breg in the Black Forest?

Answer: breg


Question: In which Dickens novel do 'Bitzer', 'Sleary', and 'James Harthouse' appear?

Answer:
charles dickens