TASK DEFINITION: Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.
PROBLEM: doriva (born 28 may 1972) is a former brazilian football player.

SOLUTION: doriva

PROBLEM: an electronic book (also called an e-book, ebook or digital book) is a book in digital form.

SOLUTION: e-book

PROBLEM: malaysia airlines flight 370 (mh370, also named under a codeshare agreement as china southern airlines flight cz748) is a missing malaysia airlines international passenger flight.

SOLUTION:
malaysia airlines flight 370