jun 1, 1990 - 1990
June 1 - President Bush and President Gorbachev sign new protocols to the Threshold Test Ban treaty.
September 25 - U.S. ratifies the Threshold Test Ban Treaty.
September 27 - The last Pershing II missile is removed from West Germany
December 11 - The Threshold Test Ban Treaty enters into force.
Added to timeline:
atomic and nuclear physics