FILE - In this Oct. 19, 1972 file photo, European leaders pose for a photograph, at the European Common Market summit conference, with French President Georges Pompidou fourth from right stands next to Britain's Prime Minister Edward Heath, third from right, at an Elysee Palace luncheon, in Paris. Britain voted in a referendum Thursday, June 23, 2016 to leave the European Union. Britain was not included when the precursor to the EU was formed following World War II, but finally joined the group, known at the time as the European Economic Community, or the Common Market, on Jan. 1, 1973. The Associated Press is making its original coverage from that day available with photos. (AP Photo/Michel Lipchitz, File)