TASK DEFINITION: Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
PROBLEM: Who has written a series of novels, entitled The Dark Tower, of which the first, in 1982, was entitled, The Gunslinger?

SOLUTION: the dark tower

PROBLEM: Forty hours before he committed suicide in 1945 Adolf Hitler married whom?

SOLUTION: adolf hitler

PROBLEM: Bankstown Airport is in which Australian state?

SOLUTION:
bankstown airport