WARSAW, July 8, 2016 (Xinhua) -- NATO Secretary General Jens Stoltenberg(R, front) and Polish President Andrzej Duda (L, front) watch the air show during the opening ceremony of the NATO summit in Warsaw, Poland on July 8, 2016. The NATO summit kicked off here Friday afternoon, with Polish President Andrzej Duda and NATO Secretary General Jens Stoltenberg officially greeting participants at the National Stadium PGE. (Xinhua/Shi Zhongyu)
