– Strikes start in Poland (Ursus, Radom, Płock) after communists raise food prices; they end on June 30. June 26 – The CN Tower is opened in Toronto, the tallest free-standing land structure opens to the public. June 27 G-6 is renamed "Group of 7" (G-7) with the inclusion of Canada. Palestinian militants hijack an Air France plane in Greece with 246 passengers and 12 crew. They take it to Entebbe, Uganda. June 28 Inauguration of the north lane of the Rodovia dos Imigrantes. June 29 Seychelles gains independence from the United Kingdom. The Conference of Communist and Workers Parties of Europe convenes in East Berlin. July July 2 – North Vietnam dissolves the Provisional Government of South Vietnam and unites the two countries to form the Socialist Republic of Vietnam. July 3 Gregg v. Georgia: The Supreme Court of the United States rules that the death penalty is not inherently cruel or unusual and is a constitutionally acceptable form of punishment overturning the Furman v. Georgia case of 1972. The great heat wave in the United Kingdom, which is currently suffering from drought conditions, reaches its peak. July 4 The U.S. celebrates its bicentennial, in recognition of the 200th anniversary of the 1776 adoption of the United States Declaration of Independence from the United Kingdom. Entebbe Raid: Israeli airborne commandos free 103 hostages being held by Palestinian hijackers of an Air France plane at Uganda's Entebbe Airport; Yonatan Netanyahu and several Ugandan soldiers are killed in the raid. July 6 – The first class of women is inducted at the United States Naval Academy in Annapolis, Maryland. July 7 German left-wing women terrorists Monika Berberich, Gabriella Rollnick, Juliane Plambeck and Inge Viett escape from the Lehrter Straße maximum security prison in West Berlin. David Steel becomes leader of the UK's Liberal Party in the aftermath of the scandal which forced out Jeremy Thorpe. July 10 Four mercenaries, three British and one American, are shot by firing squad in Angola, following the Luanda Trial. Seveso disaster: An explosion in Seveso, Italy, causes extended pollution to a large area in the neighborhood of Milan, with many evacuations and a large number of people affected by the toxic cloud. July 12 – In the United States: California State University, Fullerton massacre: seven people are shot and killed, and two others are wounded in a mass shooting on campus at California State University,