Drivers push cars to gas station during “oil crisis”, Roslindale, Boston, Massachusetts, 1973. (Photo by Spencer Grant/Getty Images)

An elephant enjoys its back being scrubbed by the keeper on March 1, 1950. (Photo by Fox Photos/Getty Images)

A Chesterfield Borough Police telephone operator tests a gasmask with built in earpiece and microphone. The telephone service is considered one of the most important links in the coordination of ARP operations and must remain operational during air raids, 12th April 1939. (Photo by Fox Photos/Hulton Archive/Getty Images)

A tow car for the children's “Grand Prix” races which take place in a parking lot in Livonia, Michigan a suburb of Detroit, circa 1955. (Photo by Three Lions/Getty Images)

A protester aims a sling shot at police in Santiago, Chile, September 1989. (Photo by Marco Ugarte/AP Photo)

American actress Shelley Duvall poses for photographers at the 30th Cannes Film Festival in France, May 27, 1977. Duvall, whose wide-eyed, winsome presence was a mainstay in the films of Robert Altman and who co-starred in Stanley Kubrick's “The Shining”, has died. She was 75. (Photo by Jean-Jacques Levy/AP Photo)

A screen shows the new Automated Target Recognition software as a TSA employee, who couldn't provide her name, waits to walk into the advanced imaging technology unit to demostrate the new software that has been installed at Miami International Airport on August 23, 2011 in Miami, Florida. The new software is designed to enhance passenger privacy by eliminating passenger-specific images and instead auto-detecting potential threat items and indicating their location on a screen which shows a generic outline of a person. (Photo by Joe Raedle/Getty Images)