Soviet Army soldiers sit on their tanks in front of the Czechoslovak Radio station building in central Prague during the first day of Soviet-led invasion to then Czechoslovakia on August 21, 1968. (Photo by Libor Hajsky/Reuters)

A policewoman uses her mobile phone as navy honor guards stand near of a World War Two memorial during celebrations to mark Victory Day in the Black Sea port of Odessa May 9, 2014. Ukraine celebrates the 1945 victory over Nazi Germany during World War Two on May 9. (Photo by Gleb Garanich/Reuters)

An Armatix employee holds a “smart gun” by the company at the Armatix headquarters in Munich May 14, 2014. The gun is implanted with an electronic chip that allows it to be fired only if the shooter is wearing a watch that communicates with it through a radio signal. If the gun is moved more than 10 inches (25 cm) from the watch, it will not fire. A Maryland gun shop owner has dropped his plan to be the first in the United States to sell the so-called “smart gun” after a backlash that included death threats. (Photo by Michael Dalder/Reuters)

Inês Carvalho (C), accompanied by her sister and cousin, is helped by her aunt to dress up at Alfama neighborhood in Lisbon on June 12, 2014. Carvalho, 18, is one of the revelers from the Alfama march and every Saint Anthony's day, Lisbon's protector, she parades with several other typical neighborhoods of the city. (Photo by Patricia De Melo Moreira/AFP Photo)

“Theyyam”. Preparation for the Theyyam performance in the surroundings of Kasaragod city. Theyyam is a popular ritual dance form of North Kerala, particularly in Kannur and Kasargod districts. The Theyyam represents a mythological, divine or heroic character. Make up of Theyyams is done by specialist. There are different types of face painting for which primarily and secondary colours are used. Therefore it is essential that the makeup man should have perfect knowledge of primary and secondary colour combinations. Sometimes, it takes several hours to paint each face. Photo location: Kasaragod, India. (Photo and caption by Rafal Ziejewski/National Geographic Photo Contest)

Collided passenger train cars are seen in Taebaek, South Korea, Tuesday, July 22, 2014. Two passenger trains collided head-on in eastern South Korea on Tuesday afternoon, killing one passenger and injuring dozens, fire officials said. (Photo by AFP Photo/Yonhap)

An Iraqi man cooks traditional Masgouf fish on a barbecue for sale in the Karada market July 02, 2014. Masgouf, one of the national dishes of Iraq is a grilled carp seasoned with olive oil, rock salt, tamarind and ground turmeric. (Photo by Scott Nelson for the Washington Post)

A woman falls while slipping on ice during freezing rain on Roosevelt Island, a borough of Manhattan, in New York January 5, 2014. New York City was hit on Friday by the first severe winter storm of 2014 and was still in the grip of sub-freezing weather on Sunday morning. The woman got up and walked away from the fall. (Photo by Zoran Milich/Reuters)