Policewomen take a picture inside a tunnel under the Chao Phraya river at a Mass Rapid Transit subway station in Bangkok, Thailand, December 14, 2015. (Photo by Athit Perawongmetha/Reuters)

Evel Knievel is shown in his rocket before his failed attempt at a highly promoted 3/4-mile leap across Snake River Canyon in Twin Falls, Idaho, on September 8, 1974. The jump failed when the parachute on his rocket malfunctioned, opening prematurely. Knievel was uninjured. (Photo by AP Photo)

An Indian soldier from the international peace keeping force (IPKF) instructs young Sri Lankan recruits in shooting, part of the training given to the citizen's volunteer force in the North-Eastern Sri Lankan city of Batticaloa, September 28, 1989. (Photo by Barbara Walton/AP Photo)

Londoners sleep on the platform and on the train tracks at Aldwych Underground station,London, during heavy all night Nazi bombing raids, October 8, 1940. (Photo by AP Photo)

An ethnic Kayaw couple Mu Htoo and her husband Htaw Eili rest at their home at Htaykho village in the Kayah state, Myanmar September 12, 2015. With about 30,000 members, the Kayaw are one of the smallest ethnic minorities among Myanmar's 135 groups. Their village has for decades been off-limits, as armed rebels fought the military before a recent ceasefire stopped the bloody conflict here. The rebels in the area have put down their guns and taken to the hills to grow rice and corn, but slash-and-burn cultivation methods mean they struggle to find new places to farm. (Photo by Soe Zeya Tun/Reuters)

People dance Tuesday, April 28, 2015, in Baltimore. Maryland's governor vowed there would be no repeat of the looting, arson and vandalism that erupted Monday in some of the city's poorest neighborhoods. (Photo by Matt Rourke/AP Photo)

Tank crew standing in front of M-4 tank, Ft. Knox, Kentucky, June, 1942. (Alfred Palmer/OWI/LOC)