Corporate credit unions are united on a cooperative basis in the Central Credit Union (US Central Credit Union). Like the credit cooperatives, credit unions form associations of a higher level, which are called corporate credit unions. Typically new members of the credit union become citizens having suretyship or recommendations from their friends - members of the credit union. The main advantage of credit unions consists in transparency, controllability, governance for shareholders. The relationship between credit unions and shareholders arise from the membership and are not customer relationship. In the UK, credit unions are a source of financing of people groups. This tool is not widely used.