Utilize the input text as a context reference, choose the right relationship between Eurozone and euro from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Eurozone leaders were also due to hold an emergency summit on Tuesday, and several of them had described the vote as an in-out decision on Greece's euro membership.

Answer: currency