1) The concept of federalism involves the division of powers between a central government and regional or local governments, allowing for shared governance and autonomy for different levels of administration.

2) The book series "The Chronicles of Narnia" by C.S. Lewis has sold over 100 million copies worldwide.

3) The Federal Reserve System, often referred to as the Fed, is the central banking system of the United States.

4) The Atlantic Ocean is the second-largest ocean and is known for its strong ocean currents, including the Gulf Stream.