A house built on a rock on the river Drina is seen near the western Serbian town of Bajina Basta, about 160km (99 miles) from the capital Belgrade May 22, 2013. The house was built in 1968 by a group of young men who decided that the rock on the river was an ideal place for a tiny shelter, according to the house's co-owner, who was among those involved in its construction. (Photo by Marko Djurica/Reuters)

Ammunition airlift into besieged Khe Sanh, Operation Pegasus, April 1968. (Photo by Larry Burrows/AP Photo)

Hooded demonstrators vandalise a shop window in Mexico City, during the commemoration of the 50th anniversary of the 1968 Tlatelolco student massacre, on October 2, 2018. Fifty years ago, Mexican troops opened fire on student demonstrators, killing hundreds just days before Mexico City hosted the 1968 Olympics – one of the darkest episodes in a year of global turbulence. (Photo by Ronaldo Schemidt/AFP Photo)

English fashion designer Mary Quant (R) with a group of models at Heathrow Airport, before leaving for a continental fashion tour, 18th March 1968. (Photo by Express/Getty Images)

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)

English actress Diana Rigg as “Emma Peel” is tied to a railway track as a miniature train advances on her in a scene from the television series “The Avengers” in 1968. Rigg died at her home in London on 10 September 2020, at the age of 82. (Photo by Popperfoto via Getty Images/Getty Images)

British fashion designer Mary Quant, right, waves as she poses with models wearing her Mod creations in Little Rock, Ark. on October 25, 1968. The models, from left, are, Amanda Tear, Rory Davis and Penny Yates. (Photo by AP Photo)

A full size working replica of the pink limousine used by Parker to chauffeur Lady Penelope in Gerry Anderson's television series “Thunderbirds”, unveiled at Woburn Abbey. United Kingdom, 27th May 1968. (Photo by Jim Gray/Keystone/Getty Images)