Children learn how to have an afternoon nap on their desk at a kindergarten in Bozhou, Anhui province, on March 21, 2013. World Sleep Day falls on March 21 this year. [Photo by Liu Qinli/Asianewsphoto]

Chinese dancers perform during a concert opening the "Year of Chinese Tourism in Russia", which is being attended by Chinese President Xi Jinping and his Russian counterpart Vladimir Putin, at the State Kremlin Palace in Moscow, on March 22, 2013. [Photo/Xinhua]