Question: What are the notes issued by the current central bank of the country Amin visited twice?

full_context: Document 1: Federal Reserve Act: The Federal Reserve Act (ch. 6, 38 Stat. 251, enacted December 23, 1913, 12 U.S.C. § § 221 to 522) is an Act of Congress that created and established the Federal Reserve System (the central banking system of the United States), and which created the authority to issue Federal Reserve Notes (commonly known as the US Dollar) as legal tender. The Act was signed into law by President Woodrow Wilson.
Document 2: Abdul Fattah Ismail: He served as Chairman of the Presidium of the Supreme People's Council (head of state) and founder, chief ideologue, and first leader of the Yemeni Socialist Party from 21 December 1978 to 21 April 1980. He was summarily executed on 13 January 1986 along with three others, allegedly for "plotting to overthrow" Ali Nasir Muhammad's regime.
Document 3: Large denominations of United States currency: Large denominations of United States currency greater than $100 were circulated by the United States Treasury until 1969. Since then, U.S. dollar banknotes have only been issued in seven denominations: $1, $2, $5, $10, $20, $50, and $100.
Document 4: United States dollar: The U.S. Constitution provides that Congress shall have the power to "borrow money on the credit of the United States". Congress has exercised that power by authorizing Federal Reserve Banks to issue Federal Reserve Notes. Those notes are "obligations of the United States" and "shall be redeemed in lawful money on demand at the Treasury Department of the United States, in the city of Washington, District of Columbia, or at any Federal Reserve bank". Federal Reserve Notes are designated by law as "legal tender" for the payment of debts. Congress has also authorized the issuance of more than 10 other types of banknotes, including the United States Note and the Federal Reserve Bank Note. The Federal Reserve Note is the only type that remains in circulation since the 1970s.
Document 5: Federal Reserve Act: The Federal Reserve Act (ch. 6, 38 Stat. 251, enacted December 23, 1913, 12 U.S.C. ch. 3) is an Act of Congress that created and established the Federal Reserve System, the central banking system of the United States, and which created the authority to issue Federal Reserve Notes (now commonly known as the U.S. Dollar) and Federal Reserve Bank Notes as legal tender. The Act was signed into law by President Woodrow Wilson.
Document 6: Husain al-Radi: Husain Ar-Radi (1924, Najaf – 24 February 1963, Baghdad), also known as Hashiim, 'Ammar, and Salam Adil, was an Iraqi communist politician as well as a poet and painter. He was the leader of the Iraqi Communist Party from 1955 until his death by execution or under torture after the Baathist coup in 1963.
Document 7: United States dollar: The Constitution provides that "a regular Statement and Account of the Receipts and Expenditures of all public Money shall be published from time to time". That provision of the Constitution is made specific by Section 331 of Title 31 of the United States Code. The sums of money reported in the "Statements" are currently being expressed in U.S. dollars (for example, see the 2009 Financial Report of the United States Government). The U.S. dollar may therefore be described as the unit of account of the United States.
Document 8: United States debt ceiling: Under Article I Section 8 of the United States Constitution, only Congress can authorize the borrowing of money on the credit of the United States. From the founding of the United States until 1917, Congress directly authorized each individual debt issued. To provide more flexibility to finance the United States' involvement in World War I, Congress modified the method by which it authorized debt in the Second Liberty Bond Act of 1917. Under this Act, Congress established an aggregate limit, or ``ceiling, ''on the total amount of new bonds that could be issued.
Document 9: United States dollar: The value of the U.S. dollar declined significantly during wartime, especially during the American Civil War, World War I, and World War II. The Federal Reserve, which was established in 1913, was designed to furnish an "elastic" currency subject to "substantial changes of quantity over short periods", which differed significantly from previous forms of high-powered money such as gold, national bank notes, and silver coins. Over the very long run, the prior gold standard kept prices stable—for instance, the price level and the value of the U.S. dollar in 1914 was not very different from the price level in the 1880s. The Federal Reserve initially succeeded in maintaining the value of the U.S. dollar and price stability, reversing the inflation caused by the First World War and stabilizing the value of the dollar during the 1920s, before presiding over a 30% deflation in U.S. prices in the 1930s.
Document 10: Charlie Wilson (Texas politician): In 1980, Wilson read an Associated Press dispatch on the congressional wires describing the refugees fleeing Soviet-occupied Afghanistan. The communist Democratic Republic of Afghanistan had taken over power during the Saur Revolution and asked the Soviet Union to help suppress resistance from the Mujahideen. According to biographer George Crile III, Wilson called the staff of the United States House Committee on Appropriations dealing with "black appropriations" and requested a two-fold appropriation increase for Afghanistan. Because Wilson had just been named to the House Appropriations Subcommittee on Defense (which is responsible for funding CIA operations), his request went through.
Document 11: Soviet–Afghan War: That operation began at 19: 00 hr., when the KGB - led Soviet Zenith Group destroyed Kabul's communications hub, paralyzing Afghan military command. At 19: 15, the assault on Tajbeg Palace began; as planned, president Hafizullah Amin was killed. Simultaneously, other objectives were occupied (e.g., the Ministry of Interior at 19: 15). The operation was fully complete by the morning of December 28, 1979.
Document 12: Federal Reserve: The Federal Reserve System (also known as the Federal Reserve or simply the Fed) is the central banking system of the United States. It was created on December 23, 1913, with the enactment of the Federal Reserve Act, after a series of financial panics (particularly the panic of 1907) led to the desire for central control of the monetary system in order to alleviate financial crises. Over the years, events such as the Great Depression in the 1930s and the Great Recession during the 2000s have led to the expansion of the roles and responsibilities of the Federal Reserve System.
Document 13: United States dollar: The Constitution of the United States of America provides that the United States Congress has the power "To coin money". Laws implementing this power are currently codified at 31 U.S.C. § 5112. Section 5112 prescribes the forms, in which the United States dollars should be issued. These coins are both designated in Section 5112 as "legal tender" in payment of debts. The Sacagawea dollar is one example of the copper alloy dollar. The pure silver dollar is known as the American Silver Eagle. Section 5112 also provides for the minting and issuance of other coins, which have values ranging from one cent to 50 dollars. These other coins are more fully described in Coins of the United States dollar.
Document 14: Hafizullah Amin: Hafizullah Amin (Pashto/Dari: حفيظ الله امين‎; born 1 August 1929 – 27 December 1979) was an Afghan communist politician during the Cold War. Amin was born in Paghman and educated at Kabul University, after which he started his career as a teacher. After a few years in that occupation, he went to the United States to study. He would visit the United States a second time before moving permanently to Afghanistan, and starting his career in radical politics. He ran as a candidate in the 1965 parliamentary election but failed to secure a seat. Amin was the only Khalqist elected to parliament in the 1969 parliamentary election, thus increasing his standing within the party. He was one of the leading organizers of the Saur Revolution which overthrew the government of Mohammad Daoud Khan. In 1979 he named himself president, prime minister, and chairman of the Khalq wing. He has been described as "ruthless" and a "radical Marxist".Amin's short-lived presidency was marked by controversies from beginning to end. He came to power by disposing of his predecessor Nur Muhammad Taraki and later ordering his death. Amin made attempts to win support from those who revolted against the communist regime which had begun under Taraki, but his government was unable to solve this problem. Many Afghans held Amin responsible for the regime's harshest measures, such as ordering thousands of executions. Thousands of people disappeared without trace during his time in office. The Soviet Union, which was dissatisfied with Amin, intervened in Afghanistan while invoking the Twenty-Year Treaty of Friendship between Afghanistan and the Soviet Union. Amin was assassinated by the Soviets on December 27, 1979 as part of Operation Storm-333, having ruled for slightly longer than three months.
Document 15: Federal Reserve: The Federal Reserve System (also known as the Federal Reserve or simply the Fed) is the central banking system of the United States of America. It was created on December 23, 1913, with the enactment of the Federal Reserve Act, after a series of financial panics (particularly the panic of 1907) led to the desire for central control of the monetary system in order to alleviate financial crises. Over the years, events such as the Great Depression in the 1930s and the Great Recession during the 2000s have led to the expansion of the roles and responsibilities of the Federal Reserve System.
ground_truth: obligations of the United States
sub_queries: Where did Amin visit for the second time? Answer: United States
the current central bank of United States is Answer: Federal Reserve
What are the notes issued by Federal Reserve ? Answer: obligations of the United States