Task: Question Generation
Input (English): The Alma-Ata Protocol also addressed other issues, including UN membership. Notably, Russia was authorized to assume the Soviet Union's UN membership, including its permanent seat on the Security Council. The Soviet Ambassador to the UN delivered a letter signed by Russian President Yeltsin to the UN Secretary-General dated December 24, 1991, informing him that by virtue of the Alma-Ata Protocol, Russia was the successor state to the USSR. After being circulated among the other UN member states, with no objection raised, the statement was declared accepted on the last day of the year, December 31, 1991.
Output (English): Who wrote the letter to the UN secretary general informing them that Russia would be replacing the USSR?