In the U.S., credit unions have a clear organizational structure. All credit unions belong to one or the other parent credit union (there are 35 of them in the U.S.). National Credit Union Administration (NCUA) - an independent federal agency, based in Washington (State of Columbia), established by the U.S. Congress to oversee the federal credit union system. The relationship of shareholders with credit union are not client-based, they are co-operative, based on different principles and standards, in particular, on the principles of the law of obligations. Worldwide credit union movement is represented by regional confederations and national organizations within the World Council of Credit Unions. A potential new member of a credit union must submit a recommendation of shareholders in which the referee becomes a warrant of a future member of the credit union.