Mikhail Gorbachev, the last leader of the Soviet Union and the 1990 Nobel Peace Prize laureate, has died, Tass news agency reported Tuesday, quoting his hospital. He was 91.Known for his reforms of political and economic systems under the concept of "perestroika," or restructuring, in the 1980s, Gorbachev declared the end of the Cold War with then U.S. President George Bush at a meeting in Malta in December 1989.He assumed the post of Soviet president in March 1990 and won the Nobel Peace Prize the same year for his central role in the East-West peace process, an achievement that shaped mod…READ FULL ARTICLE