
Serbia's (L-R) Novak Djokovic, Viktor Troicki, Dusan Lajovic and Nenad Zimonjic listen to the national anthem during opening ceremony of Serbia vs Spain Davis Cup quarterfinal tennis match in Belgrade on April 7, 2017. (Xinhua/Predrag Milosavljevic)

Serbia's (L-R) Novak Djokovic, Viktor Troicki, Dusan Lajovic and Nenad Zimonjic listen to the national anthem during opening ceremony of Serbia vs Spain Davis Cup quarterfinal tennis match in Belgrade on April 7, 2017. (Xinhua/Predrag Milosavljevic)