Given a document, find the main entity about whom the author is writing. Write the full name if mentioned in the text. Note that URLs in the text have been replaced with [Link].

[Q]: He âs back!
Legendary talk show host  David Letterman âs new Netflix show  âMy Next Guest Needs No Introduction â debuts Jan. 12  and former President Barack Obama is slated to be the first guest.
âI had a show for a long time and then I didnât have a show for a long time  and I canât tell you how great it is to be out of the damn house â  Letterman  jokes in the trailer.
The trailer doesnât indicate what  Letterman  and Obama will talk about  but itâs possible the current administration will be a hot topic on the series considering  Letterman  has spoken out against President Donald Trump.
[A]: David Letterman


[Q]: (CNN) The President has excoriated football players who have joined a protest movement by former 49ers quarterback Colin Kaepernick as unpatriotic. But the President is overlooking history -- which shows athletes now lauded as heroes  like  Jackie Robinson and Muhammad Ali   raising  their  voices (or taking a seat) in protests similar to Kaepernick's.
 Jackie Robinson   rightfully celebrated for showing enormous grace under pressure while breaking baseball's color line  refused to stand for the National Anthem after  his  playing days.
Jackie Robinson as a Brooklyn Dodger.
As  he  described in  his  1972 autobiography   Robinson -- like contemporary NFL players --  was protesting against institutional racism.  He  was expressing  his  feelings of alienation from America's system of racial apartheid.
 Robinson 's pugnacious brand of civil rights activism set the stage for succeeding generations of black athletes. Eleven-time NBA champion Bill Russell emerged as one of the most outspoken civil rights advocates of the 1960s  at a time when the city he played in  Boston  represented one of the most racially segregated cities in the North.
Above all  black American athletes are citizens  fathers  brothers  husbands and sons who have a right and responsibility to continue a long struggle for dignity exemplified by Jackie Robinson  Bill Russell and many others.
[A]: Jackie Robinson


[Q]: Rihanna  has emerged as the unlikely inspiration behind Arsenal's thumping 5-1 win against Everton.
 The singer  was at the Emirates to watch the match and enjoy the Gunner's work  work  work  work  work ethic.
After the match   she  posed with midfielder  Mesut Ozil  who described  her  as the team's "lucky charm".
The German said he was "still unbeaten with Riri" - a reference to when  she  came to watch the 2014 World Cup Final between Germany and Argentina.
Ozil himself couldn't get on the scoresheet but with  Rihanna  pulling the inspirational strings during a pre-match meet and greet  other players stepped up.
It's just a shame that whoever was looking after  her  social accounts still referred to the game as "soccer".
After the game  manager Arsene Wenger seemed to play down the importance of  Rihanna 's contribution  focusing instead on his side's "penetration and sharper game".
Given Arsenal's up and down season  there are probably high level talks with  Rihanna 's people to see if  her  schedule allows any more trips to watch the team - with one eye surely on  their  next Europa League match  away at Ostersunds FK.
[A]:
Rihanna