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Video - Argentina defend football gold
Argentina retained their Olympic men's football title as they overcame the heat to beat Nigeria 1-0 in the Bird's Nest stadium.
Benfica striker Angel di Maria's neat chip after 58 minutes was enough to give the Argentines victory.
Nigeria had their fair share of chances, but were unable to beat goalkeeper Sergio Romero.
Play was stopped twice to allow players to take on water to deal with the searing 42C (107F) heat.
Striker Lionel Messi put di Maria through on goal, after freeing himself from some tight Nigerian marking.
Nigeria were attempting to repeat their 1996 Olympic victory over Argentina, but despite some early solid defending could not keep Messi at bay.
They said play the game at noon which I don't think was a good idea
Nigeria coach Samson Siasia
"Maybe the heat was a factor," said Argentina coach Sergio Batista. "I think it the game had been played in another part of the day it would have been very different.
"We tried to make sure that we didn't get uptight, just to play our own game. We wanted to play with intelligence and move the ball around and not run around so much. We wanted the ball to do the work."
Nigeria coach Samson Siasia was critical of the decision to play the game in the middle of the day.
"No team has actually played at noon since we started this tournament," said Siasia. "It affected both countries and most players didn't perform to their level because of the heat.
"But we didn't make the rules. They said play the game at noon which I don't think was a good idea.
"We had a lot of chances on goal, but you have to score goals to win gold medals. After gold, I think silver is not bad. Look at Brazil, they came third."
Brazil took the bronze medal on Friday, strolling to a 3-0 win over Belgium.