Question: What sport did Robert Lindstedt and Alex O'Brien play?

Related documents: [0]  [DOC] Robert Lindstedt (born 19 March 1977) is a Swedish professional tennis player, who turned pro in 1998, and is a doubles specialist. His biggest title has been the 2014 Australian Open with partner Łukasz Kubot. He is also a three-time Wimbledon finalist with former partner Horia Tecău. [END] 
[1]  [DOC] Alex O'Brien (born March 7, 1970 in Amarillo, Texas) is a retired professional tennis player from the United States, who competed on the ATP Tour. He became the world No. 1 doubles player in May 2000 and was ranked as high as world No. 30 in singles in June 1997. [END]  
Answer: tennis
tennis