In this March 22, 1975 file photo, a refugee clutches a baby as a government helicopter gunship carries them away near Tuy Hoa, Vietnam, 235 miles northeast of Saigon. They were among thousands fleeing from Communist advances. AP Photographer Nick Ut will be retiring from the AP in March 2017 after 51 years of taking photographs from the front lines of the Vietnam War to the red carpets of Hollywood. (Photo by Nick Ut/AP Photo)

High-rise buildings are partly covered by heavy fog at Hong Kong's Victoria Harbour Monday, March 20, 2017. Fog blanketing Hong Kong is common in springtime and may greatly affect shipping and aviation. (Photo by Vincent Yu/AP Photo)

A dog sits in a plastic basin filled with water in Taipei, Taiwan, 05 May 2018. Betel nut seller Mr Luo, the dog's owner, said he puts his dog Ah Dai (Stupid Guy) in the water-filled basin whenever the weather get hot. Luo has a dozen pairs of glasses for Ah Dai, so the dog wears different glasses every day and many tourists take photos of Ah Dai. (Photo by David Chang/EPA/EFE)

Hindu devotees laugh as they watch the religious festival of Lathmar Holi, where women beat the men with sticks, in the town of Barsana in the Uttar Pradesh region of India, March 17, 2016. During Lathmar Holi the women of Barsana beat the men from Nandgaon, the hometown of Krishna, with wooden sticks in response to their teasing. (Photo by Cathal McNaughton/Reuters)

The Aurora Borealis (Northern Lights) is seen over the sky near the village of Pallas (Muonio region) of Lapland, Finland September 8, 2017. (Photo by Alexander Kuznetsov/Reuters)

James Brady and a police officer are seen lying on the ground after being shot while the suspect John Hinckley Jr. is apprehended,at right, moments after the attempted assassination of President Ronald Reagan, Washington, DC, March 30, 1981. (Photo by Dirck Halstead/Getty Images)

Yakutsk, with a population of around 270,000, holds its own title: that of the coldest city on Earth. Here: Frost-encrusted house in the city centre. (Photo by Amos Chapple/Courtesy Images/RFE/RL)

A tourist poses next to a tiger before officials start moving tigers from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. Wildlife authorities raid a Buddhist temple that has more than 100 tigers, taking away three cats and vowing to confiscate scores more in response to global pressure over wildlife trafficking. (Photo by Chaiwat Subprasom/Reuters)